diff --git a/.eslintrc.js b/.eslintrc.js
index 6fd40eb9f7..72cadf8138 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -87,6 +87,7 @@ module.exports = {
                 // We don't need super strict typing in test utilities
                 "@typescript-eslint/explicit-function-return-type": "off",
                 "@typescript-eslint/explicit-member-accessibility": "off",
+                "@typescript-eslint/ban-ts-comment": "off",
             },
         },
     ],
diff --git a/package.json b/package.json
index 6a4fcfbb25..dd664704bc 100644
--- a/package.json
+++ b/package.json
@@ -68,7 +68,7 @@
         "@types/react": "17.0.58"
     },
     "dependencies": {
-        "@matrix-org/olm": "https://gitlab.matrix.org/api/v4/projects/27/packages/npm/@matrix-org/olm/-/@matrix-org/olm-3.2.12.tgz",
+        "@matrix-org/olm": "https://gitlab.matrix.org/api/v4/projects/27/packages/npm/@matrix-org/olm/-/@matrix-org/olm-3.2.14.tgz",
         "@matrix-org/react-sdk-module-api": "^0.0.4",
         "gfm.css": "^1.1.2",
         "jsrsasign": "^10.5.25",
@@ -104,6 +104,7 @@
         "@svgr/webpack": "^5.5.0",
         "@testing-library/react": "^12.1.5",
         "@types/jest": "^29.0.0",
+        "@types/jitsi-meet": "^2.0.2",
         "@types/jsrsasign": "^10.5.4",
         "@types/modernizr": "^3.5.3",
         "@types/node": "^16",
diff --git a/src/@types/jitsi-meet.d.ts b/src/@types/jitsi-meet.d.ts
new file mode 100644
index 0000000000..a5680debde
--- /dev/null
+++ b/src/@types/jitsi-meet.d.ts
@@ -0,0 +1,29 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import "jitsi-meet";
+
+declare module "jitsi-meet" {
+    interface ExternalAPIEventCallbacks {
+        errorOccurred: (e: { error: Error & { isFatal?: boolean } }) => void;
+    }
+
+    interface JitsiMeetExternalAPI {
+        executeCommand(command: "setTileView", value: boolean): void;
+    }
+}
+
+export as namespace Jitsi;
diff --git a/src/async-components/structures/CompatibilityView.tsx b/src/async-components/structures/CompatibilityView.tsx
index 02bcffa443..dde0aea256 100644
--- a/src/async-components/structures/CompatibilityView.tsx
+++ b/src/async-components/structures/CompatibilityView.tsx
@@ -17,10 +17,10 @@ limitations under the License.
 import * as React from "react";
 import { _t } from "matrix-react-sdk/src/languageHandler";
 import SdkConfig from "matrix-react-sdk/src/SdkConfig";
-
 // directly import the style here as this layer does not support rethemedex at this time so no matrix-react-sdk
 // PostCSS variables will be accessible.
 import "../../../res/css/structures/ErrorView.pcss";
+import { ReactNode } from "react";
 
 interface IProps {
     onAccept(): void;
@@ -91,7 +91,7 @@ const CompatibilityView: React.FC<IProps> = ({ onAccept }) => {
         android = [];
     }
 
-    let mobileHeader = <h2 id="step2_heading">{_t("Use %(brand)s on mobile", { brand })}</h2>;
+    let mobileHeader: ReactNode = <h2 id="step2_heading">{_t("Use %(brand)s on mobile", { brand })}</h2>;
     if (!android.length && !ios) {
         mobileHeader = null;
     }
diff --git a/src/components/views/auth/VectorAuthPage.tsx b/src/components/views/auth/VectorAuthPage.tsx
index 560fe424aa..e04dfcefd7 100644
--- a/src/components/views/auth/VectorAuthPage.tsx
+++ b/src/components/views/auth/VectorAuthPage.tsx
@@ -20,7 +20,7 @@ import SdkConfig from "matrix-react-sdk/src/SdkConfig";
 import VectorAuthFooter from "./VectorAuthFooter";
 
 export default class VectorAuthPage extends React.PureComponent {
-    private static welcomeBackgroundUrl;
+    private static welcomeBackgroundUrl?: string;
 
     // cache the url as a static to prevent it changing without refreshing
     private static getWelcomeBackgroundUrl(): string {
diff --git a/src/favicon.ts b/src/favicon.ts
index 5a9516d24a..9f4fbec392 100644
--- a/src/favicon.ts
+++ b/src/favicon.ts
@@ -72,14 +72,14 @@ export default class Favicon {
                 // get height and width of the favicon
                 this.canvas.height = this.baseImage.height > 0 ? this.baseImage.height : 32;
                 this.canvas.width = this.baseImage.width > 0 ? this.baseImage.width : 32;
-                this.context = this.canvas.getContext("2d");
+                this.context = this.canvas.getContext("2d")!;
                 this.ready();
             };
-            this.baseImage.setAttribute("src", lastIcon.getAttribute("href"));
+            this.baseImage.setAttribute("src", lastIcon.getAttribute("href")!);
         } else {
             this.canvas.height = this.baseImage.height = 32;
             this.canvas.width = this.baseImage.width = 32;
-            this.context = this.canvas.getContext("2d");
+            this.context = this.canvas.getContext("2d")!;
             this.ready();
         }
     }
@@ -239,7 +239,7 @@ export default class Favicon {
         const icons: HTMLLinkElement[] = [];
         const links = window.document.getElementsByTagName("head")[0].getElementsByTagName("link");
         for (const link of links) {
-            if (/(^|\s)icon(\s|$)/i.test(link.getAttribute("rel"))) {
+            if (link.hasAttribute("rel") && /(^|\s)icon(\s|$)/i.test(link.getAttribute("rel")!)) {
                 icons.push(link);
             }
         }
diff --git a/src/vector/app.tsx b/src/vector/app.tsx
index 6614948abd..2b140a5ba7 100644
--- a/src/vector/app.tsx
+++ b/src/vector/app.tsx
@@ -25,7 +25,7 @@ import React, { ReactElement } from "react";
 import PlatformPeg from "matrix-react-sdk/src/PlatformPeg";
 import { UserFriendlyError } from "matrix-react-sdk/src/languageHandler";
 import AutoDiscoveryUtils from "matrix-react-sdk/src/utils/AutoDiscoveryUtils";
-import { AutoDiscovery } from "matrix-js-sdk/src/autodiscovery";
+import { AutoDiscovery, ClientConfig } from "matrix-js-sdk/src/autodiscovery";
 import * as Lifecycle from "matrix-react-sdk/src/Lifecycle";
 import SdkConfig, { parseSsoRedirectOptions } from "matrix-react-sdk/src/SdkConfig";
 import { IConfigOptions } from "matrix-react-sdk/src/IConfigOptions";
@@ -33,6 +33,8 @@ import { logger } from "matrix-js-sdk/src/logger";
 import { createClient } from "matrix-js-sdk/src/matrix";
 import { SnakedObject } from "matrix-react-sdk/src/utils/SnakedObject";
 import MatrixChat from "matrix-react-sdk/src/components/structures/MatrixChat";
+import { ValidatedServerConfig } from "matrix-react-sdk/src/utils/ValidatedServerConfig";
+import { QueryDict, encodeParams } from "matrix-js-sdk/src/utils";
 
 import { parseQs } from "./url_utils";
 import VectorBasePlatform from "./platform/VectorBasePlatform";
@@ -55,24 +57,19 @@ window.matrixLogger = logger;
 // If we're in electron, we should never pass through a file:// URL otherwise
 // the identity server will try to 302 the browser to it, which breaks horribly.
 // so in that instance, hardcode to use app.element.io for now instead.
-function makeRegistrationUrl(params: object): string {
-    let url;
+function makeRegistrationUrl(params: QueryDict): string {
+    let url: string;
     if (window.location.protocol === "vector:") {
         url = "https://app.element.io/#/register";
     } else {
         url = window.location.protocol + "//" + window.location.host + window.location.pathname + "#/register";
     }
 
-    const keys = Object.keys(params);
-    for (let i = 0; i < keys.length; ++i) {
-        if (i === 0) {
-            url += "?";
-        } else {
-            url += "&";
-        }
-        const k = keys[i];
-        url += k + "=" + encodeURIComponent(params[k]);
+    const encodedParams = encodeParams(params);
+    if (encodedParams) {
+        url += "?" + encodedParams;
     }
+
     return url;
 }
 
@@ -117,18 +114,19 @@ export async function loadApp(fragParams: {}): Promise<ReactElement> {
     if (!hasPossibleToken && !isReturningFromSso && autoRedirect) {
         logger.log("Bypassing app load to redirect to SSO");
         const tempCli = createClient({
-            baseUrl: config.validated_server_config.hsUrl,
-            idBaseUrl: config.validated_server_config.isUrl,
+            baseUrl: config.validated_server_config!.hsUrl,
+            idBaseUrl: config.validated_server_config!.isUrl,
         });
-        PlatformPeg.get().startSingleSignOn(tempCli, "sso", `/${getScreenFromLocation(window.location).screen}`);
+        PlatformPeg.get()!.startSingleSignOn(tempCli, "sso", `/${getScreenFromLocation(window.location).screen}`);
 
         // We return here because startSingleSignOn() will asynchronously redirect us. We don't
         // care to wait for it, and don't want to show any UI while we wait (not even half a welcome
         // page). As such, just don't even bother loading the MatrixChat component.
-        return;
+        return <React.Fragment />;
     }
 
-    const defaultDeviceName = snakedConfig.get("default_device_display_name") ?? platform.getDefaultDeviceDisplayName();
+    const defaultDeviceName =
+        snakedConfig.get("default_device_display_name") ?? platform?.getDefaultDeviceDisplayName();
 
     return (
         <MatrixChat
@@ -146,7 +144,7 @@ export async function loadApp(fragParams: {}): Promise<ReactElement> {
 }
 
 async function verifyServerConfig(): Promise<IConfigOptions> {
-    let validatedConfig;
+    let validatedConfig: ValidatedServerConfig;
     try {
         logger.log("Verifying homeserver configuration");
 
@@ -197,7 +195,7 @@ async function verifyServerConfig(): Promise<IConfigOptions> {
             }
         }
 
-        let discoveryResult = null;
+        let discoveryResult: ClientConfig | undefined;
         if (wkConfig) {
             logger.log("Config uses a default_server_config - validating object");
             discoveryResult = await AutoDiscovery.fromDiscoveryConfig(wkConfig);
diff --git a/src/vector/getconfig.ts b/src/vector/getconfig.ts
index 4633b57d8d..17a897809d 100644
--- a/src/vector/getconfig.ts
+++ b/src/vector/getconfig.ts
@@ -18,16 +18,16 @@ import type { IConfigOptions } from "matrix-react-sdk/src/IConfigOptions";
 
 // Load the config file. First try to load up a domain-specific config of the
 // form "config.$domain.json" and if that fails, fall back to config.json.
-export async function getVectorConfig(relativeLocation = ""): Promise<IConfigOptions> {
+export async function getVectorConfig(relativeLocation = ""): Promise<IConfigOptions | undefined> {
     if (relativeLocation !== "" && !relativeLocation.endsWith("/")) relativeLocation += "/";
 
-    const specificConfigPromise = getConfig(`${relativeLocation}config.${document.domain}.json`);
+    const specificConfigPromise = getConfig(`${relativeLocation}config.${window.location.hostname}.json`);
     const generalConfigPromise = getConfig(relativeLocation + "config.json");
 
     try {
         const configJson = await specificConfigPromise;
         // 404s succeed with an empty json config, so check that there are keys
-        if (Object.keys(configJson).length === 0) {
+        if (!configJson || Object.keys(configJson).length === 0) {
             throw new Error(); // throw to enter the catch
         }
         return configJson;
@@ -36,7 +36,7 @@ export async function getVectorConfig(relativeLocation = ""): Promise<IConfigOpt
     }
 }
 
-async function getConfig(configJsonFilename: string): Promise<IConfigOptions> {
+async function getConfig(configJsonFilename: string): Promise<IConfigOptions | undefined> {
     const url = new URL(configJsonFilename, window.location.href);
     url.searchParams.set("cachebuster", Date.now().toString());
     const res = await fetch(url, {
diff --git a/src/vector/index.ts b/src/vector/index.ts
index dcffa5e2cc..56d87e4fd0 100644
--- a/src/vector/index.ts
+++ b/src/vector/index.ts
@@ -71,7 +71,7 @@ function checkBrowserFeatures(): boolean {
     // ES2019: http://262.ecma-international.org/10.0/#sec-object.fromentries
     window.Modernizr.addTest("objectfromentries", () => typeof window.Object?.fromEntries === "function");
 
-    const featureList = Object.keys(window.Modernizr);
+    const featureList = Object.keys(window.Modernizr) as Array<keyof ModernizrStatic>;
 
     let featureComplete = true;
     for (const feature of featureList) {
@@ -240,7 +240,7 @@ start().catch((err) => {
     logger.error(err);
     // show the static error in an iframe to not lose any context / console data
     // with some basic styling to make the iframe full page
-    delete document.body.style.height;
+    document.body.style.removeProperty("height");
     const iframe = document.createElement("iframe");
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-ignore - typescript seems to only like the IE syntax for iframe sandboxing
@@ -254,5 +254,5 @@ start().catch((err) => {
     iframe.style.right = "0";
     iframe.style.bottom = "0";
     iframe.style.border = "0";
-    document.getElementById("matrixchat").appendChild(iframe);
+    document.getElementById("matrixchat")?.appendChild(iframe);
 });
diff --git a/src/vector/init.tsx b/src/vector/init.tsx
index 6ab4e4cacf..a255c7d7f0 100644
--- a/src/vector/init.tsx
+++ b/src/vector/init.tsx
@@ -67,7 +67,7 @@ export async function loadConfig(): Promise<void> {
     // granular settings are loaded correctly and to avoid duplicating the override logic for the theme.
     //
     // Note: this isn't called twice for some wrappers, like the Jitsi wrapper.
-    const platformConfig = await PlatformPeg.get().getConfig();
+    const platformConfig = await PlatformPeg.get()?.getConfig();
     if (platformConfig) {
         SdkConfig.put(platformConfig);
     } else {
@@ -119,7 +119,7 @@ export function loadOlm(): Promise<void> {
 
 export async function loadLanguage(): Promise<void> {
     const prefLang = SettingsStore.getValue("language", null, /*excludeDefault=*/ true);
-    let langs = [];
+    let langs: string[] = [];
 
     if (!prefLang) {
         languageHandler.getLanguagesFromBrowser().forEach((l) => {
@@ -163,7 +163,7 @@ export async function showError(title: string, messages?: string[]): Promise<voi
     );
 }
 
-export async function showIncompatibleBrowser(onAccept): Promise<void> {
+export async function showIncompatibleBrowser(onAccept: () => void): Promise<void> {
     const CompatibilityView = (
         await import(
             /* webpackChunkName: "compatibility-view" */
diff --git a/src/vector/jitsi/index.ts b/src/vector/jitsi/index.ts
index 77379fe209..f50fa0d8d4 100644
--- a/src/vector/jitsi/index.ts
+++ b/src/vector/jitsi/index.ts
@@ -30,6 +30,14 @@ import { IConfigOptions } from "matrix-react-sdk/src/IConfigOptions";
 import { SnakedObject } from "matrix-react-sdk/src/utils/SnakedObject";
 import { ElementWidgetCapabilities } from "matrix-react-sdk/src/stores/widgets/ElementWidgetCapabilities";
 
+import type {
+    JitsiMeetExternalAPIConstructor,
+    ExternalAPIEventCallbacks,
+    JitsiMeetExternalAPI as _JitsiMeetExternalAPI,
+    AudioMuteStatusChangedEvent,
+    LogEvent,
+    VideoMuteStatusChangedEvent,
+} from "jitsi-meet";
 import { getVectorConfig } from "../getconfig";
 
 // We have to trick webpack into loading our CSS for us.
@@ -40,7 +48,7 @@ const JITSI_OPENIDTOKEN_JWT_AUTH = "openidtoken-jwt";
 // Dev note: we use raw JS without many dependencies to reduce bundle size.
 // We do not need all of React to render a Jitsi conference.
 
-declare let JitsiMeetExternalAPI: any;
+declare let JitsiMeetExternalAPI: JitsiMeetExternalAPIConstructor;
 
 let inConference = false;
 
@@ -60,8 +68,8 @@ let isVideoChannel: boolean;
 let supportsScreensharing: boolean;
 let language: string;
 
-let widgetApi: WidgetApi;
-let meetApi: any; // JitsiMeetExternalAPI
+let widgetApi: WidgetApi | undefined;
+let meetApi: _JitsiMeetExternalAPI | undefined;
 let skipOurWelcomeScreen = false;
 
 const setupCompleted = (async (): Promise<string | void> => {
@@ -102,12 +110,12 @@ const setupCompleted = (async (): Promise<string | void> => {
         }
 
         // Set this up as early as possible because Element will be hitting it almost immediately.
-        let widgetApiReady: Promise<void>;
+        let widgetApiReady: Promise<void> | undefined;
         if (parentUrl && widgetId) {
             const parentOrigin = new URL(qsParam("parentUrl")).origin;
             widgetApi = new WidgetApi(qsParam("widgetId"), parentOrigin);
 
-            widgetApiReady = new Promise<void>((resolve) => widgetApi.once("ready", resolve));
+            widgetApiReady = new Promise<void>((resolve) => widgetApi!.once("ready", resolve));
             widgetApi.requestCapabilities(VideoConferenceCapabilities);
 
             // jitsi cannot work in a popup if auth token is provided because widgetApi is not available there
@@ -122,7 +130,7 @@ const setupCompleted = (async (): Promise<string | void> => {
                 action: WidgetApiAction,
                 handler: (request: IWidgetApiRequestData) => Promise<void>,
             ): void => {
-                widgetApi.on(`action:${action}`, async (ev: CustomEvent<IWidgetApiRequest>) => {
+                widgetApi!.on(`action:${action}`, async (ev: CustomEvent<IWidgetApiRequest>) => {
                     ev.preventDefault();
                     await setupCompleted;
 
@@ -138,7 +146,7 @@ const setupCompleted = (async (): Promise<string | void> => {
                         }
                     }
 
-                    await widgetApi.transport.reply(ev.detail, response);
+                    await widgetApi!.transport.reply(ev.detail, response);
                 });
             };
 
@@ -149,7 +157,7 @@ const setupCompleted = (async (): Promise<string | void> => {
                 if (force === true) {
                     meetApi?.dispose();
                     notifyHangup();
-                    meetApi = null;
+                    meetApi = undefined;
                     closeConference();
                 } else {
                     meetApi?.executeCommand("hangup");
@@ -212,9 +220,10 @@ const setupCompleted = (async (): Promise<string | void> => {
 
         // We've reached the point where we have to wait for the config, so do that then parse it.
         const instanceConfig = new SnakedObject<IConfigOptions>((await configPromise) ?? <IConfigOptions>{});
-        const jitsiConfig = instanceConfig.get("jitsi_widget") ?? {};
-        skipOurWelcomeScreen =
-            new SnakedObject<IConfigOptions["jitsi_widget"]>(jitsiConfig).get("skip_built_in_welcome_screen") ?? false;
+        const jitsiConfig = instanceConfig.get("jitsi_widget");
+        if (jitsiConfig) {
+            skipOurWelcomeScreen = new SnakedObject(jitsiConfig).get("skip_built_in_welcome_screen") ?? false;
+        }
 
         // Either reveal the prejoin screen, or skip straight to Jitsi depending on the config.
         // We don't set up the call yet though as this might lead to failure without the widget API.
@@ -232,12 +241,12 @@ const setupCompleted = (async (): Promise<string | void> => {
         enableJoinButton(); // always enable the button
     } catch (e) {
         logger.error("Error setting up Jitsi widget", e);
-        document.getElementById("widgetActionContainer").innerText = "Failed to load Jitsi widget";
+        document.getElementById("widgetActionContainer")!.innerText = "Failed to load Jitsi widget";
     }
 })();
 
 function enableJoinButton(): void {
-    document.getElementById("joinButton").onclick = (): Promise<void> => joinConference();
+    document.getElementById("joinButton")!.onclick = (): Promise<void> => joinConference();
 }
 
 function switchVisibleContainers(): void {
@@ -251,9 +260,9 @@ function switchVisibleContainers(): void {
 }
 
 function toggleConferenceVisibility(inConference: boolean): void {
-    document.getElementById("jitsiContainer").style.visibility = inConference ? "unset" : "hidden";
+    document.getElementById("jitsiContainer")!.style.visibility = inConference ? "unset" : "hidden";
     // Video rooms have a separate UI for joining, so they should never show our join button
-    document.getElementById("joinButtonContainer").style.visibility =
+    document.getElementById("joinButtonContainer")!.style.visibility =
         inConference || isVideoChannel ? "hidden" : "unset";
 }
 
@@ -311,7 +320,7 @@ async function notifyHangup(errorMessage?: string): Promise<void> {
 
 function closeConference(): void {
     switchVisibleContainers();
-    document.getElementById("jitsiContainer").innerHTML = "";
+    document.getElementById("jitsiContainer")!.innerHTML = "";
 
     if (skipOurWelcomeScreen) {
         skipToJitsiSplashScreen();
@@ -349,17 +358,17 @@ function mapLanguage(language: string): string {
 // and a non-nullish input specifies the label of a specific device to use.
 // Same for video inputs.
 async function joinConference(audioInput?: string | null, videoInput?: string | null): Promise<void> {
-    let jwt;
+    let jwt: string | undefined;
     if (jitsiAuth === JITSI_OPENIDTOKEN_JWT_AUTH) {
         // See https://github.com/matrix-org/prosody-mod-auth-matrix-user-verification
-        const openIdToken: IOpenIDCredentials = await widgetApi.requestOpenIDConnectToken();
+        const openIdToken = await widgetApi?.requestOpenIDConnectToken();
         logger.log("Got OpenID Connect token");
 
-        if (!openIdToken.access_token) {
+        if (!openIdToken?.access_token) {
             // eslint-disable-line camelcase
             // We've failing to get a token, don't try to init conference
             logger.warn("Expected to have an OpenID credential, cannot initialize widget.");
-            document.getElementById("widgetActionContainer").innerText = "Failed to load Jitsi widget";
+            document.getElementById("widgetActionContainer")!.innerText = "Failed to load Jitsi widget";
             return;
         }
         jwt = createJWTToken(openIdToken);
@@ -376,7 +385,7 @@ async function joinConference(audioInput?: string | null, videoInput?: string |
     const options = {
         width: "100%",
         height: "100%",
-        parentNode: document.querySelector("#jitsiContainer"),
+        parentNode: document.querySelector("#jitsiContainer") ?? undefined,
         roomName: conferenceId,
         devices: {
             audioInput,
@@ -434,13 +443,13 @@ async function joinConference(audioInput?: string | null, videoInput?: string |
     // (regardless of video on or off)
     meetApi.on("videoConferenceJoined", onVideoConferenceJoined);
     meetApi.on("videoConferenceLeft", onVideoConferenceLeft);
-    meetApi.on("readyToClose", closeConference);
+    meetApi.on("readyToClose", closeConference as ExternalAPIEventCallbacks["readyToClose"]);
     meetApi.on("errorOccurred", onErrorOccurred);
     meetApi.on("audioMuteStatusChanged", onAudioMuteStatusChanged);
     meetApi.on("videoMuteStatusChanged", onVideoMuteStatusChanged);
 
-    ["videoConferenceJoined", "participantJoined", "participantLeft"].forEach((event) => {
-        meetApi.on(event, updateParticipants);
+    (["videoConferenceJoined", "participantJoined", "participantLeft"] as const).forEach((event) => {
+        meetApi!.on(event, updateParticipants);
     });
 
     // Patch logs into rageshakes
@@ -456,9 +465,9 @@ const onVideoConferenceJoined = (): void => {
     // We can't just use these commands immediately after creating the
     // iframe, because there's *another* bug where they can crash Jitsi by
     // racing with its startup process.
-    if (displayName) meetApi.executeCommand("displayName", displayName);
+    if (displayName) meetApi?.executeCommand("displayName", displayName);
     // This doesn't have a userInfo equivalent, so has to be set via commands
-    if (avatarUrl) meetApi.executeCommand("avatarUrl", avatarUrl);
+    if (avatarUrl) meetApi?.executeCommand("avatarUrl", avatarUrl);
 
     if (widgetApi) {
         // ignored promise because we don't care if it works
@@ -468,30 +477,30 @@ const onVideoConferenceJoined = (): void => {
     }
 
     // Video rooms should start in tile mode
-    if (isVideoChannel) meetApi.executeCommand("setTileView", true);
+    if (isVideoChannel) meetApi?.executeCommand("setTileView", true);
 };
 
 const onVideoConferenceLeft = (): void => {
     notifyHangup();
-    meetApi = null;
+    meetApi = undefined;
 };
 
-const onErrorOccurred = ({ error }): void => {
+const onErrorOccurred = ({ error }: Parameters<ExternalAPIEventCallbacks["errorOccurred"]>[0]): void => {
     if (error.isFatal) {
         // We got disconnected. Since Jitsi Meet might send us back to the
         // prejoin screen, we're forced to act as if we hung up entirely.
         notifyHangup(error.message);
-        meetApi = null;
+        meetApi = undefined;
         closeConference();
     }
 };
 
-const onAudioMuteStatusChanged = ({ muted }): void => {
+const onAudioMuteStatusChanged = ({ muted }: AudioMuteStatusChangedEvent): void => {
     const action = muted ? ElementWidgetActions.MuteAudio : ElementWidgetActions.UnmuteAudio;
     widgetApi?.transport.send(action, {});
 };
 
-const onVideoMuteStatusChanged = ({ muted }): void => {
+const onVideoMuteStatusChanged = ({ muted }: VideoMuteStatusChangedEvent): void => {
     if (muted) {
         // Jitsi Meet always sends a "video muted" event directly before
         // hanging up, which we need to ignore by padding the timeout here,
@@ -507,8 +516,9 @@ const onVideoMuteStatusChanged = ({ muted }): void => {
 
 const updateParticipants = (): void => {
     widgetApi?.transport.send(ElementWidgetActions.CallParticipants, {
-        participants: meetApi.getParticipantsInfo(),
+        participants: meetApi?.getParticipantsInfo(),
     });
 };
 
-const onLog = ({ logLevel, args }): void => (parent as unknown as typeof global).mx_rage_logger?.log(logLevel, ...args);
+const onLog = ({ logLevel, args }: LogEvent): void =>
+    (parent as unknown as typeof global).mx_rage_logger?.log(logLevel, ...args);
diff --git a/src/vector/mobile_guide/index.ts b/src/vector/mobile_guide/index.ts
index 0a0a351eef..5f93440748 100644
--- a/src/vector/mobile_guide/index.ts
+++ b/src/vector/mobile_guide/index.ts
@@ -31,17 +31,17 @@ function renderConfigError(message: string): void {
 }
 
 async function initPage(): Promise<void> {
-    document.getElementById("back_to_element_button").onclick = onBackToElementClick;
+    document.getElementById("back_to_element_button")!.onclick = onBackToElementClick;
 
     const config = await getVectorConfig("..");
 
     // We manually parse the config similar to how validateServerConfig works because
     // calling that function pulls in roughly 4mb of JS we don't use.
 
-    const wkConfig = config["default_server_config"]; // overwritten later under some conditions
-    const serverName = config["default_server_name"];
-    const defaultHsUrl = config["default_hs_url"];
-    const defaultIsUrl = config["default_is_url"];
+    const wkConfig = config?.["default_server_config"]; // overwritten later under some conditions
+    const serverName = config?.["default_server_name"];
+    const defaultHsUrl = config?.["default_hs_url"];
+    const defaultIsUrl = config?.["default_is_url"];
 
     const incompatibleOptions = [wkConfig, serverName, defaultHsUrl].filter((i) => !!i);
     if (incompatibleOptions.length > 1) {
@@ -54,13 +54,13 @@ async function initPage(): Promise<void> {
         return renderConfigError("Invalid configuration: no default server specified.");
     }
 
-    let hsUrl = "";
-    let isUrl = "";
+    let hsUrl: string | undefined;
+    let isUrl: string | undefined;
 
-    if (wkConfig && wkConfig["m.homeserver"]) {
+    if (typeof wkConfig?.["m.homeserver"]?.["base_url"] === "string") {
         hsUrl = wkConfig["m.homeserver"]["base_url"];
 
-        if (wkConfig["m.identity_server"]) {
+        if (typeof wkConfig["m.identity_server"]?.["base_url"] === "string") {
             isUrl = wkConfig["m.identity_server"]["base_url"];
         }
     }
@@ -96,17 +96,19 @@ async function initPage(): Promise<void> {
     if (isUrl && !isUrl.endsWith("/")) isUrl += "/";
 
     if (hsUrl !== "https://matrix.org/") {
-        (document.getElementById("configure_element_button") as HTMLAnchorElement).href =
-            "https://mobile.element.io?hs_url=" + encodeURIComponent(hsUrl) + "&is_url=" + encodeURIComponent(isUrl);
-        document.getElementById("step1_heading").innerHTML = "1: Install the app";
-        document.getElementById("step2_container").style.display = "block";
-        document.getElementById("hs_url").innerText = hsUrl;
+        let url = "https://mobile.element.io?hs_url=" + encodeURIComponent(hsUrl);
 
         if (isUrl) {
-            document.getElementById("custom_is").style.display = "block";
-            document.getElementById("is_url").style.display = "block";
-            document.getElementById("is_url").innerText = isUrl;
+            document.getElementById("custom_is")!.style.display = "block";
+            document.getElementById("is_url")!.style.display = "block";
+            document.getElementById("is_url")!.innerText = isUrl;
+            url += "&is_url=" + encodeURIComponent(isUrl ?? "");
         }
+
+        (document.getElementById("configure_element_button") as HTMLAnchorElement).href = url;
+        document.getElementById("step1_heading")!.innerHTML = "1: Install the app";
+        document.getElementById("step2_container")!.style.display = "block";
+        document.getElementById("hs_url")!.innerText = hsUrl;
     }
 }
 
diff --git a/src/vector/platform/ElectronPlatform.tsx b/src/vector/platform/ElectronPlatform.tsx
index 537ce4cc04..b18b1abe4e 100644
--- a/src/vector/platform/ElectronPlatform.tsx
+++ b/src/vector/platform/ElectronPlatform.tsx
@@ -79,7 +79,7 @@ function platformFriendlyName(): string {
 function onAction(payload: ActionPayload): void {
     // Whitelist payload actions, no point sending most across
     if (["call_state"].includes(payload.action)) {
-        window.electron.send("app_onAction", payload);
+        window.electron!.send("app_onAction", payload);
     }
 }
 
@@ -105,6 +105,10 @@ export default class ElectronPlatform extends VectorBasePlatform {
     public constructor() {
         super();
 
+        if (!window.electron) {
+            throw new Error("Cannot instantiate ElectronPlatform, window.electron is not set");
+        }
+
         dis.register(onAction);
         /*
             IPC Call `check_updates` returns:
@@ -135,12 +139,12 @@ export default class ElectronPlatform extends VectorBasePlatform {
             const key = `DOWNLOAD_TOAST_${id}`;
 
             const onAccept = (): void => {
-                window.electron.send("userDownloadAction", { id, open: true });
+                window.electron!.send("userDownloadAction", { id, open: true });
                 ToastStore.sharedInstance().dismissToast(key);
             };
 
             const onDismiss = (): void => {
-                window.electron.send("userDownloadAction", { id });
+                window.electron!.send("userDownloadAction", { id });
             };
 
             ToastStore.sharedInstance().addOrReplaceToast({
@@ -164,7 +168,7 @@ export default class ElectronPlatform extends VectorBasePlatform {
         BreadcrumbsStore.instance.on(UPDATE_EVENT, this.onBreadcrumbsUpdate);
     }
 
-    public async getConfig(): Promise<IConfigOptions> {
+    public async getConfig(): Promise<IConfigOptions | undefined> {
         return this.ipc.call("getConfig");
     }
 
@@ -212,7 +216,7 @@ export default class ElectronPlatform extends VectorBasePlatform {
         if (this.notificationCount === count) return;
         super.setNotificationCount(count);
 
-        window.electron.send("setBadgeCount", count);
+        window.electron!.send("setBadgeCount", count);
     }
 
     public supportsNotifications(): boolean {
@@ -252,7 +256,7 @@ export default class ElectronPlatform extends VectorBasePlatform {
     }
 
     public loudNotification(ev: MatrixEvent, room: Room): void {
-        window.electron.send("loudNotification");
+        window.electron!.send("loudNotification");
     }
 
     public needsUrlTooltips(): boolean {
@@ -288,14 +292,14 @@ export default class ElectronPlatform extends VectorBasePlatform {
 
     public startUpdateCheck(): void {
         super.startUpdateCheck();
-        window.electron.send("check_updates");
+        window.electron!.send("check_updates");
     }
 
     public installUpdate(): void {
         // IPC to the main process to install the update, since quitAndInstall
         // doesn't fire the before-quit event so the main process needs to know
         // it should exit.
-        window.electron.send("install_update");
+        window.electron!.send("install_update");
     }
 
     public getDefaultDeviceDisplayName(): string {
diff --git a/src/vector/platform/IPCManager.ts b/src/vector/platform/IPCManager.ts
index 868f528d3e..2ad4a25565 100644
--- a/src/vector/platform/IPCManager.ts
+++ b/src/vector/platform/IPCManager.ts
@@ -33,6 +33,9 @@ export class IPCManager {
         private readonly sendChannel: ElectronChannel = "ipcCall",
         private readonly recvChannel: ElectronChannel = "ipcReply",
     ) {
+        if (!window.electron) {
+            throw new Error("Cannot instantiate ElectronPlatform, window.electron is not set");
+        }
         window.electron.on(this.recvChannel, this.onIpcReply);
     }
 
@@ -42,7 +45,7 @@ export class IPCManager {
         const deferred = defer<any>();
         this.pendingIpcCalls[ipcCallId] = deferred;
         // Maybe add a timeout to these? Probably not necessary.
-        window.electron.send(this.sendChannel, { id: ipcCallId, name, args });
+        window.electron!.send(this.sendChannel, { id: ipcCallId, name, args });
         return deferred.promise;
     }
 
diff --git a/src/vector/platform/SeshatIndexManager.ts b/src/vector/platform/SeshatIndexManager.ts
index 3526bcc464..dd77d58002 100644
--- a/src/vector/platform/SeshatIndexManager.ts
+++ b/src/vector/platform/SeshatIndexManager.ts
@@ -19,6 +19,7 @@ import BaseEventIndexManager, {
     IEventAndProfile,
     IIndexStats,
     ISearchArgs,
+    ILoadArgs,
 } from "matrix-react-sdk/src/indexing/BaseEventIndexManager";
 import { IMatrixProfile, IEventWithRoomId as IMatrixEvent, IResultRoomEvents } from "matrix-js-sdk/src/@types/search";
 
@@ -75,7 +76,7 @@ export class SeshatIndexManager extends BaseEventIndexManager {
         return this.ipc.call("removeCrawlerCheckpoint", checkpoint);
     }
 
-    public async loadFileEvents(args): Promise<IEventAndProfile[]> {
+    public async loadFileEvents(args: ILoadArgs): Promise<IEventAndProfile[]> {
         return this.ipc.call("loadFileEvents", args);
     }
 
diff --git a/src/vector/platform/VectorBasePlatform.ts b/src/vector/platform/VectorBasePlatform.ts
index cbb3b9eeb5..fccb6119c9 100644
--- a/src/vector/platform/VectorBasePlatform.ts
+++ b/src/vector/platform/VectorBasePlatform.ts
@@ -30,7 +30,7 @@ import Favicon from "../../favicon";
 export default abstract class VectorBasePlatform extends BasePlatform {
     protected _favicon: Favicon;
 
-    public async getConfig(): Promise<IConfigOptions> {
+    public async getConfig(): Promise<IConfigOptions | undefined> {
         return getVectorConfig();
     }
 
diff --git a/src/vector/platform/WebPlatform.ts b/src/vector/platform/WebPlatform.ts
index 938fc8fd88..75eae03e8f 100644
--- a/src/vector/platform/WebPlatform.ts
+++ b/src/vector/platform/WebPlatform.ts
@@ -40,6 +40,8 @@ function getNormalizedAppVersion(version: string): string {
 }
 
 export default class WebPlatform extends VectorBasePlatform {
+    private static readonly VERSION = process.env.VERSION!; // baked in by Webpack
+
     public constructor() {
         super();
         // Register service worker if available on this platform
@@ -101,7 +103,7 @@ export default class WebPlatform extends VectorBasePlatform {
     }
 
     public getAppVersion(): Promise<string> {
-        return Promise.resolve(getNormalizedAppVersion(process.env.VERSION));
+        return Promise.resolve(getNormalizedAppVersion(WebPlatform.VERSION));
     }
 
     public startUpdater(): void {
@@ -113,7 +115,7 @@ export default class WebPlatform extends VectorBasePlatform {
         //
         // Ideally, loading an old copy would be impossible with the
         // cache-control: nocache HTTP header set, but Firefox doesn't always obey it :/
-        console.log("startUpdater, current version is " + getNormalizedAppVersion(process.env.VERSION));
+        console.log("startUpdater, current version is " + getNormalizedAppVersion(WebPlatform.VERSION));
         this.pollForUpdate((version: string, newVersion: string) => {
             const query = parseQs(location);
             if (query.updated) {
@@ -144,7 +146,7 @@ export default class WebPlatform extends VectorBasePlatform {
     ): Promise<UpdateStatus> => {
         return this.getMostRecentVersion().then(
             (mostRecentVersion) => {
-                const currentVersion = getNormalizedAppVersion(process.env.VERSION);
+                const currentVersion = getNormalizedAppVersion(WebPlatform.VERSION);
 
                 if (currentVersion !== mostRecentVersion) {
                     if (this.shouldShowUpdate(mostRecentVersion)) {
diff --git a/src/vector/routing.ts b/src/vector/routing.ts
index 92b2c7a59b..04d455f51f 100644
--- a/src/vector/routing.ts
+++ b/src/vector/routing.ts
@@ -22,7 +22,7 @@ import MatrixChatType from "matrix-react-sdk/src/components/structures/MatrixCha
 
 import { parseQsFromFragment } from "./url_utils";
 
-let lastLocationHashSet: string = null;
+let lastLocationHashSet: string | null = null;
 
 export function getScreenFromLocation(location: Location): { screen: string; params: QueryDict } {
     const fragparts = parseQsFromFragment(location);
diff --git a/test/app-tests/loading-test.tsx b/test/app-tests/loading-test.tsx
index b57695df1a..e5805e66ed 100644
--- a/test/app-tests/loading-test.tsx
+++ b/test/app-tests/loading-test.tsx
@@ -28,6 +28,8 @@ import MockHttpBackend from "matrix-mock-request";
 import { ValidatedServerConfig } from "matrix-react-sdk/src/utils/ValidatedServerConfig";
 import { IndexedDBCryptoStore } from "matrix-js-sdk/src/crypto/store/indexeddb-crypto-store";
 import { QueryDict, sleep } from "matrix-js-sdk/src/utils";
+import { IConfigOptions } from "matrix-react-sdk/src/IConfigOptions";
+import { ActionPayload } from "matrix-react-sdk/src/dispatcher/payloads";
 
 import "../jest-mocks";
 import WebPlatform from "../../src/vector/platform/WebPlatform";
@@ -38,26 +40,21 @@ const DEFAULT_HS_URL = "http://my_server";
 const DEFAULT_IS_URL = "http://my_is";
 
 describe("loading:", function () {
-    let parentDiv;
-    let httpBackend;
+    let httpBackend: MockHttpBackend;
 
     // an Object simulating the window.location
     let windowLocation: Location | undefined;
 
     // the mounted MatrixChat
-    let matrixChat: RenderResult<any, any, any> | undefined;
+    let matrixChat: RenderResult | undefined;
 
     // a promise which resolves when the MatrixChat calls onTokenLoginCompleted
     let tokenLoginCompletePromise: Promise<void> | undefined;
 
     beforeEach(function () {
         httpBackend = new MockHttpBackend();
+        // @ts-ignore
         window.fetch = httpBackend.fetchFn;
-        parentDiv = document.createElement("div");
-
-        // uncomment this to actually add the div to the UI, to help with
-        // debugging (but slow things down)
-        // document.body.appendChild(parentDiv);
 
         windowLocation = undefined;
         matrixChat = undefined;
@@ -80,8 +77,13 @@ describe("loading:", function () {
      * TODO: it would be nice to factor some of this stuff out of index.js so
      * that we can test it rather than our own implementation of it.
      */
-    function loadApp(opts?): void {
-        opts = opts || {};
+    function loadApp(
+        opts: {
+            queryString?: string;
+            uriFragment?: string;
+            config?: IConfigOptions;
+        } = {},
+    ): void {
         const queryString = opts.queryString || "";
         const uriFragment = opts.uriFragment || "";
 
@@ -93,7 +95,7 @@ describe("loading:", function () {
             },
         } as Location;
 
-        function onNewScreen(screen): void {
+        function onNewScreen(screen: string): void {
             console.log(Date.now() + " newscreen " + screen);
             const hash = "#/" + screen;
             windowLocation!.hash = hash;
@@ -102,7 +104,7 @@ describe("loading:", function () {
 
         // Parse the given window.location and return parameters that can be used when calling
         // MatrixChat.showScreen(screen, params)
-        function getScreenFromLocation(location): { screen: string; params: QueryDict } {
+        function getScreenFromLocation(location: Location): { screen: string; params: QueryDict } {
             const fragparts = parseQsFromFragment(location);
             return {
                 screen: fragparts.location.substring(1),
@@ -112,22 +114,20 @@ describe("loading:", function () {
 
         const fragParts = parseQsFromFragment(windowLocation);
 
-        const config = Object.assign(
-            {
-                default_hs_url: DEFAULT_HS_URL,
-                default_is_url: DEFAULT_IS_URL,
-                validated_server_config: {
-                    hsUrl: DEFAULT_HS_URL,
-                    hsName: "TEST_ENVIRONMENT",
-                    hsNameIsDifferent: false, // yes, we lie
-                    isUrl: DEFAULT_IS_URL,
-                } as ValidatedServerConfig,
-                embeddedPages: {
-                    homeUrl: "data:text/html;charset=utf-8;base64,PGh0bWw+PC9odG1sPg==",
-                },
+        const config = {
+            default_hs_url: DEFAULT_HS_URL,
+            default_is_url: DEFAULT_IS_URL,
+            validated_server_config: {
+                hsUrl: DEFAULT_HS_URL,
+                hsName: "TEST_ENVIRONMENT",
+                hsNameIsDifferent: false, // yes, we lie
+                isUrl: DEFAULT_IS_URL,
+            } as ValidatedServerConfig,
+            embedded_pages: {
+                home_url: "data:text/html;charset=utf-8;base64,PGh0bWw+PC9odG1sPg==",
             },
-            opts.config || {},
-        );
+            ...(opts.config ?? {}),
+        } as IConfigOptions;
 
         PlatformPeg.set(new WebPlatform());
 
@@ -137,18 +137,17 @@ describe("loading:", function () {
             matrixChat = render(
                 <MatrixChat
                     onNewScreen={onNewScreen}
-                    config={config}
+                    config={config!}
                     serverConfig={config.validated_server_config}
                     realQueryParams={params}
                     startingFragmentQueryParams={fragParts.params}
                     enableGuest={true}
                     onTokenLoginCompleted={resolve}
-                    initialScreenAfterLogin={getScreenFromLocation(windowLocation)}
+                    initialScreenAfterLogin={getScreenFromLocation(windowLocation!)}
                     makeRegistrationUrl={(): string => {
                         throw new Error("Not implemented");
                     }}
                 />,
-                parentDiv,
             );
         });
     }
@@ -157,15 +156,15 @@ describe("loading:", function () {
     // http requests until we do.
     //
     // returns a promise resolving to the received request
-    async function expectAndAwaitSync(opts?): Promise<any> {
-        let syncRequest = null;
+    async function expectAndAwaitSync(opts?: { isGuest?: boolean }): Promise<any> {
+        let syncRequest: (typeof MockHttpBackend.prototype.requests)[number] | null = null;
         httpBackend.when("GET", "/_matrix/client/versions").respond(200, {
             versions: ["r0.3.0"],
             unstable_features: {
                 "m.lazy_load_members": true,
             },
         });
-        const isGuest = opts && opts.isGuest;
+        const isGuest = opts?.isGuest;
         if (!isGuest) {
             // the call to create the LL filter
             httpBackend.when("POST", "/filter").respond(200, { filter_id: "llfid" });
@@ -183,7 +182,7 @@ describe("loading:", function () {
             if (syncRequest) {
                 return syncRequest;
             }
-            await httpBackend.flush();
+            await httpBackend.flush(undefined);
         }
         throw new Error("Gave up waiting for /sync");
     }
@@ -201,11 +200,11 @@ describe("loading:", function () {
                     httpBackend
                         .when("POST", "/register")
                         .check(function (req) {
-                            expect(req.queryParams.kind).toEqual("guest");
+                            expect(req.queryParams?.kind).toEqual("guest");
                         })
                         .respond(403, "Guest access is disabled");
 
-                    return httpBackend.flush();
+                    return httpBackend.flush(undefined);
                 })
                 .then(() => {
                     // Wait for another trip around the event loop for the UI to update
@@ -234,11 +233,11 @@ describe("loading:", function () {
                     httpBackend
                         .when("POST", "/register")
                         .check(function (req) {
-                            expect(req.queryParams.kind).toEqual("guest");
+                            expect(req.queryParams?.kind).toEqual("guest");
                         })
                         .respond(403, "Guest access is disabled");
 
-                    return httpBackend.flush();
+                    return httpBackend.flush(undefined);
                 })
                 .then(() => {
                     // Wait for another trip around the event loop for the UI to update
@@ -403,14 +402,14 @@ describe("loading:", function () {
                     httpBackend
                         .when("POST", "/register")
                         .check(function (req) {
-                            expect(req.queryParams.kind).toEqual("guest");
+                            expect(req.queryParams?.kind).toEqual("guest");
                         })
                         .respond(200, {
                             user_id: "@guest:localhost",
                             access_token: "secret_token",
                         });
 
-                    return httpBackend.flush();
+                    return httpBackend.flush(undefined);
                 })
                 .then(() => {
                     return awaitLoggedIn(matrixChat!);
@@ -440,14 +439,14 @@ describe("loading:", function () {
                         .when("POST", "/register")
                         .check(function (req) {
                             expect(req.path.startsWith(DEFAULT_HS_URL)).toBe(true);
-                            expect(req.queryParams.kind).toEqual("guest");
+                            expect(req.queryParams?.kind).toEqual("guest");
                         })
                         .respond(200, {
                             user_id: "@guest:localhost",
                             access_token: "secret_token",
                         });
 
-                    return httpBackend.flush();
+                    return httpBackend.flush(undefined);
                 })
                 .then(() => {
                     return awaitLoggedIn(matrixChat!);
@@ -480,14 +479,14 @@ describe("loading:", function () {
                     httpBackend
                         .when("POST", "/register")
                         .check(function (req) {
-                            expect(req.queryParams.kind).toEqual("guest");
+                            expect(req.queryParams?.kind).toEqual("guest");
                         })
                         .respond(200, {
                             user_id: "@guest:localhost",
                             access_token: "secret_token",
                         });
 
-                    return httpBackend.flush();
+                    return httpBackend.flush(undefined);
                 })
                 .then(() => {
                     return awaitLoggedIn(matrixChat!);
@@ -513,7 +512,7 @@ describe("loading:", function () {
                 httpBackend
                     .when("POST", "/register")
                     .check(function (req) {
-                        expect(req.queryParams.kind).toEqual("guest");
+                        expect(req.queryParams?.kind).toEqual("guest");
                     })
                     .respond(200, {
                         user_id: "@guest:localhost",
@@ -521,7 +520,7 @@ describe("loading:", function () {
                     });
 
                 return httpBackend
-                    .flush()
+                    .flush(undefined)
                     .then(() => {
                         return awaitLoggedIn(matrixChat!);
                     })
@@ -584,7 +583,7 @@ describe("loading:", function () {
                             access_token: "access_token",
                         });
 
-                    return httpBackend.flush();
+                    return httpBackend.flush(undefined);
                 })
                 .then(() => {
                     // at this point, MatrixChat should fire onTokenLoginCompleted, which
@@ -607,11 +606,11 @@ describe("loading:", function () {
 
     // check that we have a Login component, send a 'user:pass' login,
     // and await the HTTP requests.
-    async function completeLogin(matrixChat: RenderResult<any, any, any>): Promise<void> {
+    async function completeLogin(matrixChat: RenderResult): Promise<void> {
         // When we switch to the login component, it'll hit the login endpoint
         // for proof of life and to get flows. We'll only give it one option.
         httpBackend.when("GET", "/login").respond(200, { flows: [{ type: "m.login.password" }] });
-        httpBackend.flush(); // We already would have tried the GET /login request
+        httpBackend.flush(undefined); // We already would have tried the GET /login request
 
         // Give the component some time to finish processing the login flows before
         // continuing.
@@ -635,7 +634,7 @@ describe("loading:", function () {
         fireEvent.click(screen.getByText("Sign in", { selector: ".mx_Login_submit" }));
 
         return httpBackend
-            .flush()
+            .flush(undefined)
             .then(() => {
                 // Wait for another trip around the event loop for the UI to update
                 return sleep(1);
@@ -656,11 +655,11 @@ async function assertAtLoadingSpinner(): Promise<void> {
     await screen.findByRole("progressbar");
 }
 
-async function awaitLoggedIn(matrixChat: RenderResult<any, any, any>): Promise<void> {
+async function awaitLoggedIn(matrixChat: RenderResult): Promise<void> {
     if (matrixChat.container.querySelector(".mx_MatrixChat_wrapper")) return; // already logged in
 
     return new Promise((resolve) => {
-        const onAction = ({ action }): void => {
+        const onAction = ({ action }: ActionPayload): void => {
             if (action !== "on_logged_in") {
                 return;
             }
@@ -673,19 +672,19 @@ async function awaitLoggedIn(matrixChat: RenderResult<any, any, any>): Promise<v
     });
 }
 
-async function awaitRoomView(matrixChat?: RenderResult<any, any, any>): Promise<void> {
+async function awaitRoomView(matrixChat?: RenderResult): Promise<void> {
     await waitFor(() => matrixChat?.container.querySelector(".mx_RoomView"));
 }
 
-async function awaitLoginComponent(matrixChat?: RenderResult<any, any, any>): Promise<void> {
+async function awaitLoginComponent(matrixChat?: RenderResult): Promise<void> {
     await waitFor(() => matrixChat?.container.querySelector(".mx_AuthPage"));
 }
 
-async function awaitWelcomeComponent(matrixChat?: RenderResult<any, any, any>): Promise<void> {
+async function awaitWelcomeComponent(matrixChat?: RenderResult): Promise<void> {
     await waitFor(() => matrixChat?.container.querySelector(".mx_Welcome"));
 }
 
-function moveFromWelcomeToLogin(matrixChat?: RenderResult<any, any, any>): Promise<void> {
+function moveFromWelcomeToLogin(matrixChat?: RenderResult): Promise<void> {
     dis.dispatch({ action: "start_login" });
     return awaitLoginComponent(matrixChat);
 }
diff --git a/test/unit-tests/favicon-test.ts b/test/unit-tests/favicon-test.ts
index 8e2f45864c..4e9739db0b 100644
--- a/test/unit-tests/favicon-test.ts
+++ b/test/unit-tests/favicon-test.ts
@@ -29,7 +29,7 @@ describe("Favicon", () => {
     it("should create a link element if one doesn't yet exist", () => {
         const favicon = new Favicon();
         expect(favicon).toBeTruthy();
-        const link = window.document.querySelector("link");
+        const link = window.document.querySelector("link")!;
         expect(link.rel).toContain("icon");
     });
 
diff --git a/test/unit-tests/vector/getconfig-test.ts b/test/unit-tests/vector/getconfig-test.ts
index aac830457e..7537854172 100644
--- a/test/unit-tests/vector/getconfig-test.ts
+++ b/test/unit-tests/vector/getconfig-test.ts
@@ -21,7 +21,6 @@ import { getVectorConfig } from "../../../src/vector/getconfig";
 fetchMock.config.overwriteRoutes = true;
 
 describe("getVectorConfig()", () => {
-    const prevDocumentDomain = document.domain;
     const elementDomain = "app.element.io";
     const now = 1234567890;
     const specificConfig = {
@@ -32,7 +31,10 @@ describe("getVectorConfig()", () => {
     };
 
     beforeEach(() => {
-        document.domain = elementDomain;
+        Object.defineProperty(window, "location", {
+            value: { href: `https://${elementDomain}`, hostname: elementDomain },
+            writable: true,
+        });
 
         // stable value for cachebuster
         jest.spyOn(Date, "now").mockReturnValue(now);
@@ -41,7 +43,6 @@ describe("getVectorConfig()", () => {
     });
 
     afterAll(() => {
-        document.domain = prevDocumentDomain;
         jest.spyOn(Date, "now").mockRestore();
     });
 
@@ -107,6 +108,6 @@ describe("getVectorConfig()", () => {
 
         // We can't assert it'll be a SyntaxError as node-fetch behaves differently
         // https://github.com/wheresrhys/fetch-mock/issues/270
-        await expect(getVectorConfig()).rejects.toThrow("Unexpected token } in JSON at position 19");
+        await expect(getVectorConfig()).rejects.toThrow("in JSON at position 19");
     });
 });
diff --git a/test/unit-tests/vector/platform/ElectronPlatform-test.ts b/test/unit-tests/vector/platform/ElectronPlatform-test.ts
index 24de2e180d..653c5cf3f5 100644
--- a/test/unit-tests/vector/platform/ElectronPlatform-test.ts
+++ b/test/unit-tests/vector/platform/ElectronPlatform-test.ts
@@ -47,8 +47,7 @@ describe("ElectronPlatform", () => {
     beforeEach(() => {
         window.electron = mockElectron;
         jest.clearAllMocks();
-        delete window.navigator;
-        window.navigator = { userAgent: defaultUserAgent } as unknown as Navigator;
+        Object.defineProperty(window, "navigator", { value: { userAgent: defaultUserAgent }, writable: true });
     });
 
     const getElectronEventHandlerCall = (eventType: string): [type: string, handler: Function] | undefined =>
@@ -56,7 +55,7 @@ describe("ElectronPlatform", () => {
 
     it("flushes rageshake before quitting", () => {
         new ElectronPlatform();
-        const [event, handler] = getElectronEventHandlerCall("before-quit");
+        const [event, handler] = getElectronEventHandlerCall("before-quit")!;
         // correct event bound
         expect(event).toBeTruthy();
 
@@ -68,7 +67,7 @@ describe("ElectronPlatform", () => {
 
     it("dispatches view settings action on preferences event", () => {
         new ElectronPlatform();
-        const [event, handler] = getElectronEventHandlerCall("preferences");
+        const [event, handler] = getElectronEventHandlerCall("preferences")!;
         // correct event bound
         expect(event).toBeTruthy();
 
@@ -80,7 +79,7 @@ describe("ElectronPlatform", () => {
     describe("updates", () => {
         it("dispatches on check updates action", () => {
             new ElectronPlatform();
-            const [event, handler] = getElectronEventHandlerCall("check_updates");
+            const [event, handler] = getElectronEventHandlerCall("check_updates")!;
             // correct event bound
             expect(event).toBeTruthy();
 
@@ -93,7 +92,7 @@ describe("ElectronPlatform", () => {
 
         it("dispatches on check updates action when update not available", () => {
             new ElectronPlatform();
-            const [, handler] = getElectronEventHandlerCall("check_updates");
+            const [, handler] = getElectronEventHandlerCall("check_updates")!;
 
             handler({}, false);
             expect(dispatchSpy).toHaveBeenCalledWith({
@@ -138,8 +137,7 @@ describe("ElectronPlatform", () => {
             ["Mozilla/5.0 (X11; SunOS i686; rv:21.0) Gecko/20100101 Firefox/21.0", "Element Desktop: SunOS"],
             ["custom user agent", "Element Desktop: Unknown"],
         ])("%s = %s", (userAgent, result) => {
-            delete window.navigator;
-            window.navigator = { userAgent } as unknown as Navigator;
+            Object.defineProperty(window, "navigator", { value: { userAgent }, writable: true });
             const platform = new ElectronPlatform();
             expect(platform.getDefaultDeviceDisplayName()).toEqual(result);
         });
diff --git a/test/unit-tests/vector/platform/WebPlatform-test.ts b/test/unit-tests/vector/platform/WebPlatform-test.ts
index 6f7c332c2d..af35137f99 100644
--- a/test/unit-tests/vector/platform/WebPlatform-test.ts
+++ b/test/unit-tests/vector/platform/WebPlatform-test.ts
@@ -33,7 +33,6 @@ describe("WebPlatform", () => {
     });
 
     it("registers service worker", () => {
-        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
         // @ts-ignore - mocking readonly object
         navigator.serviceWorker = { register: jest.fn() };
         new WebPlatform();
@@ -41,10 +40,7 @@ describe("WebPlatform", () => {
     });
 
     it("should call reload on window location object", () => {
-        delete window.location;
-        window.location = {
-            reload: jest.fn(),
-        } as unknown as Location;
+        Object.defineProperty(window, "location", { value: { reload: jest.fn() }, writable: true });
 
         const platform = new WebPlatform();
         expect(window.location.reload).not.toHaveBeenCalled();
@@ -53,10 +49,7 @@ describe("WebPlatform", () => {
     });
 
     it("should call reload to install update", () => {
-        delete window.location;
-        window.location = {
-            reload: jest.fn(),
-        } as unknown as Location;
+        Object.defineProperty(window, "location", { value: { reload: jest.fn() }, writable: true });
 
         const platform = new WebPlatform();
         expect(window.location.reload).not.toHaveBeenCalled();
@@ -73,10 +66,8 @@ describe("WebPlatform", () => {
                 "develop.element.io: Chrome on macOS",
             ],
         ])("%s & %s = %s", (url, userAgent, result) => {
-            delete window.navigator;
-            window.navigator = { userAgent } as unknown as Navigator;
-            delete window.location;
-            window.location = { href: url } as unknown as Location;
+            Object.defineProperty(window, "navigator", { value: { userAgent }, writable: true });
+            Object.defineProperty(window, "location", { value: { href: url }, writable: true });
             const platform = new WebPlatform();
             expect(platform.getDefaultDeviceDisplayName()).toEqual(result);
         });
@@ -88,14 +79,12 @@ describe("WebPlatform", () => {
             permission: "notGranted",
         };
         beforeEach(() => {
-            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
             // @ts-ignore
             window.Notification = mockNotification;
             mockNotification.permission = "notGranted";
         });
 
         it("supportsNotifications returns false when platform does not support notifications", () => {
-            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
             // @ts-ignore
             window.Notification = undefined;
             expect(new WebPlatform().supportsNotifications()).toBe(false);
@@ -132,7 +121,8 @@ describe("WebPlatform", () => {
         });
 
         afterAll(() => {
-            process.env.VERSION = envVersion;
+            // @ts-ignore
+            WebPlatform.VERSION = envVersion;
         });
 
         it("should return true from canSelfUpdate()", async () => {
@@ -142,18 +132,21 @@ describe("WebPlatform", () => {
         });
 
         it("getAppVersion returns normalized app version", async () => {
-            process.env.VERSION = prodVersion;
+            // @ts-ignore
+            WebPlatform.VERSION = prodVersion;
             const platform = new WebPlatform();
 
             const version = await platform.getAppVersion();
             expect(version).toEqual(prodVersion);
 
-            process.env.VERSION = `v${prodVersion}`;
+            // @ts-ignore
+            WebPlatform.VERSION = `v${prodVersion}`;
             const version2 = await platform.getAppVersion();
             // v prefix removed
             expect(version2).toEqual(prodVersion);
 
-            process.env.VERSION = `version not like semver`;
+            // @ts-ignore
+            WebPlatform.VERSION = `version not like semver`;
             const notSemverVersion = await platform.getAppVersion();
             expect(notSemverVersion).toEqual(`version not like semver`);
         });
@@ -163,7 +156,8 @@ describe("WebPlatform", () => {
                 "should return not available and call showNoUpdate when current version " +
                     "matches most recent version",
                 async () => {
-                    process.env.VERSION = prodVersion;
+                    // @ts-ignore
+                    WebPlatform.VERSION = prodVersion;
                     fetchMock.getOnce("/version", prodVersion);
                     const platform = new WebPlatform();
 
@@ -178,7 +172,8 @@ describe("WebPlatform", () => {
             );
 
             it("should strip v prefix from versions before comparing", async () => {
-                process.env.VERSION = prodVersion;
+                // @ts-ignore
+                WebPlatform.VERSION = prodVersion;
                 fetchMock.getOnce("/version", `v${prodVersion}`);
                 const platform = new WebPlatform();
 
@@ -195,7 +190,8 @@ describe("WebPlatform", () => {
             it(
                 "should return ready and call showUpdate when current version " + "differs from most recent version",
                 async () => {
-                    process.env.VERSION = "0.0.0"; // old version
+                    // @ts-ignore
+                    WebPlatform.VERSION = "0.0.0"; // old version
                     fetchMock.getOnce("/version", prodVersion);
                     const platform = new WebPlatform();
 
@@ -210,7 +206,8 @@ describe("WebPlatform", () => {
             );
 
             it("should return ready without showing update when user registered in last 24", async () => {
-                process.env.VERSION = "0.0.0"; // old version
+                // @ts-ignore
+                WebPlatform.VERSION = "0.0.0"; // old version
                 jest.spyOn(MatrixClientPeg, "userRegisteredWithinLastHours").mockReturnValue(true);
                 fetchMock.getOnce("/version", prodVersion);
                 const platform = new WebPlatform();
diff --git a/test/unit-tests/vector/routing-test.ts b/test/unit-tests/vector/routing-test.ts
index 28676a1c89..3b8df5302d 100644
--- a/test/unit-tests/vector/routing-test.ts
+++ b/test/unit-tests/vector/routing-test.ts
@@ -18,24 +18,28 @@ import { onNewScreen } from "../../../src/vector/routing";
 
 describe("onNewScreen", () => {
     it("should replace history if stripping via fields", () => {
-        delete window.location;
-        window.location = {
-            hash: "#/room/!room:server?via=abc",
-            replace: jest.fn(),
-            assign: jest.fn(),
-        } as unknown as Location;
+        Object.defineProperty(window, "location", {
+            value: {
+                hash: "#/room/!room:server?via=abc",
+                replace: jest.fn(),
+                assign: jest.fn(),
+            },
+            writable: true,
+        });
         onNewScreen("room/!room:server");
         expect(window.location.assign).not.toHaveBeenCalled();
         expect(window.location.replace).toHaveBeenCalled();
     });
 
     it("should not replace history if changing rooms", () => {
-        delete window.location;
-        window.location = {
-            hash: "#/room/!room1:server?via=abc",
-            replace: jest.fn(),
-            assign: jest.fn(),
-        } as unknown as Location;
+        Object.defineProperty(window, "location", {
+            value: {
+                hash: "#/room/!room1:server?via=abc",
+                replace: jest.fn(),
+                assign: jest.fn(),
+            },
+            writable: true,
+        });
         onNewScreen("room/!room2:server");
         expect(window.location.assign).toHaveBeenCalled();
         expect(window.location.replace).not.toHaveBeenCalled();
diff --git a/test/unit-tests/vector/url_utils-test.ts b/test/unit-tests/vector/url_utils-test.ts
index 374b6c6d29..4b907de55d 100644
--- a/test/unit-tests/vector/url_utils-test.ts
+++ b/test/unit-tests/vector/url_utils-test.ts
@@ -17,7 +17,6 @@ limitations under the License.
 import { parseQsFromFragment, parseQs } from "../../../src/vector/url_utils";
 
 describe("url_utils.ts", function () {
-    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-ignore
     const location: Location = {
         hash: "",
diff --git a/yarn.lock b/yarn.lock
index 2c25279fd2..da364f632e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1544,9 +1544,9 @@
   resolved "https://registry.yarnpkg.com/@matrix-org/matrix-wysiwyg/-/matrix-wysiwyg-2.0.0.tgz#913eb5faa5d43c7a4ee9bda68de1aa1dcc49a11d"
   integrity sha512-xRYFwsf6Jx7KTCpwU91mVhPA8q/c+oOVyK98NnexyK/IcQS7BMFAns5GZX9b6ZEy38u30KoxeN6mxvxi+ysQgg==
 
-"@matrix-org/olm@https://gitlab.matrix.org/api/v4/projects/27/packages/npm/@matrix-org/olm/-/@matrix-org/olm-3.2.12.tgz":
-  version "3.2.12"
-  resolved "https://gitlab.matrix.org/api/v4/projects/27/packages/npm/@matrix-org/olm/-/@matrix-org/olm-3.2.12.tgz#0bce3c86f9d36a4984d3c3e07df1c3fb4c679bd9"
+"@matrix-org/olm@https://gitlab.matrix.org/api/v4/projects/27/packages/npm/@matrix-org/olm/-/@matrix-org/olm-3.2.14.tgz":
+  version "3.2.14"
+  resolved "https://gitlab.matrix.org/api/v4/projects/27/packages/npm/@matrix-org/olm/-/@matrix-org/olm-3.2.14.tgz#acd96c00a881d0f462e1f97a56c73742c8dbc984"
 
 "@matrix-org/react-sdk-module-api@^0.0.4":
   version "0.0.4"
@@ -2104,6 +2104,11 @@
     expect "^29.0.0"
     pretty-format "^29.0.0"
 
+"@types/jitsi-meet@^2.0.2":
+  version "2.0.2"
+  resolved "https://registry.yarnpkg.com/@types/jitsi-meet/-/jitsi-meet-2.0.2.tgz#4670e6dd47f2762cda5af53b73ab0a6e39ec0205"
+  integrity sha512-rnb5znCdZs7T2VgA16wyu5UHIbq+WR2HH233GPkS6HQ9m7Sh5jiXChZ41jo0tCTtNuSCziPIb5sI+6OPKK8h+Q==
+
 "@types/jsdom@^20.0.0":
   version "20.0.1"
   resolved "https://registry.yarnpkg.com/@types/jsdom/-/jsdom-20.0.1.tgz#07c14bc19bd2f918c1929541cdaacae894744808"