diff --git a/src/AddThreepid.ts b/src/AddThreepid.ts
index e115441f5c..a1567d2256 100644
--- a/src/AddThreepid.ts
+++ b/src/AddThreepid.ts
@@ -256,7 +256,7 @@ export default class AddThreepid {
             } else {
                 await this.matrixClient.addThreePid(
                     {
-                        sid: this.sessionId,
+                        sid: this.sessionId!,
                         client_secret: this.clientSecret,
                         id_server: getIdServerDomain(this.matrixClient),
                     },
@@ -377,7 +377,7 @@ export default class AddThreepid {
         } else {
             await this.matrixClient.addThreePid(
                 {
-                    sid: this.sessionId,
+                    sid: this.sessionId!,
                     client_secret: this.clientSecret,
                     id_server: getIdServerDomain(this.matrixClient),
                 },
diff --git a/src/PosthogAnalytics.ts b/src/PosthogAnalytics.ts
index dc4e483781..5924c0a768 100644
--- a/src/PosthogAnalytics.ts
+++ b/src/PosthogAnalytics.ts
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import posthog, { PostHog, Properties } from "posthog-js";
+import posthog, { CaptureOptions, PostHog, Properties } from "posthog-js";
 import { MatrixClient } from "matrix-js-sdk/src/client";
 import { logger } from "matrix-js-sdk/src/logger";
 import { UserProperties } from "@matrix-org/analytics-events/types/typescript/UserProperties";
@@ -56,10 +56,6 @@ export interface IPosthogEvent {
     $set_once?: void;
 }
 
-export interface IPostHogEventOptions {
-    timestamp?: Date;
-}
-
 export enum Anonymity {
     Disabled,
     Anonymous,
@@ -256,19 +252,13 @@ export class PosthogAnalytics {
     }
 
     // eslint-disable-nextline no-unused-vars
-    private capture(eventName: string, properties: Properties, options?: IPostHogEventOptions): void {
+    private capture(eventName: string, properties: Properties, options?: CaptureOptions): void {
         if (!this.enabled) {
             return;
         }
         const { origin, hash, pathname } = window.location;
         properties["redactedCurrentUrl"] = getRedactedCurrentLocation(origin, hash, pathname);
-        this.posthog.capture(
-            eventName,
-            { ...this.propertiesForNextEvent, ...properties },
-            // TODO: Uncomment below once https://github.com/PostHog/posthog-js/pull/391
-            // gets merged
-            /* options as any, */ // No proper type definition in the posthog library
-        );
+        this.posthog.capture(eventName, { ...this.propertiesForNextEvent, ...properties }, options);
         this.propertiesForNextEvent = {};
     }
 
@@ -342,7 +332,7 @@ export class PosthogAnalytics {
         this.setAnonymity(Anonymity.Disabled);
     }
 
-    public trackEvent<E extends IPosthogEvent>({ eventName, ...properties }: E, options?: IPostHogEventOptions): void {
+    public trackEvent<E extends IPosthogEvent>({ eventName, ...properties }: E, options?: CaptureOptions): void {
         if (this.anonymity == Anonymity.Disabled || this.anonymity == Anonymity.Anonymous) return;
         this.capture(eventName, properties, options);
     }
@@ -420,7 +410,7 @@ export class PosthogAnalytics {
         // that we want to accumulate before the user has given consent
         // All other scenarios should not track a user before they have given
         // explicit consent that they are ok with their analytics data being collected
-        const options: IPostHogEventOptions = {};
+        const options: CaptureOptions = {};
         const registrationTime = parseInt(window.localStorage.getItem("mx_registration_time")!, 10);
         if (!isNaN(registrationTime)) {
             options.timestamp = new Date(registrationTime);
diff --git a/src/components/structures/auth/ForgotPassword.tsx b/src/components/structures/auth/ForgotPassword.tsx
index c4c0834987..311fb373db 100644
--- a/src/components/structures/auth/ForgotPassword.tsx
+++ b/src/components/structures/auth/ForgotPassword.tsx
@@ -345,12 +345,15 @@ export default class ForgotPassword extends React.Component<Props, State> {
         }
     };
 
-    private onInputChanged = (stateKey: string, ev: React.FormEvent<HTMLInputElement>): void => {
+    private onInputChanged = (
+        stateKey: "email" | "password" | "password2",
+        ev: React.FormEvent<HTMLInputElement>,
+    ): void => {
         let value = ev.currentTarget.value;
         if (stateKey === "email") value = value.trim();
         this.setState({
             [stateKey]: value,
-        } as any);
+        } as Pick<State, typeof stateKey>);
     };
 
     public renderEnterEmail(): JSX.Element {
diff --git a/src/components/structures/auth/forgot-password/EnterEmail.tsx b/src/components/structures/auth/forgot-password/EnterEmail.tsx
index 653aaef233..7b82121216 100644
--- a/src/components/structures/auth/forgot-password/EnterEmail.tsx
+++ b/src/components/structures/auth/forgot-password/EnterEmail.tsx
@@ -29,7 +29,7 @@ interface EnterEmailProps {
     errorText: string | ReactNode | null;
     homeserver: string;
     loading: boolean;
-    onInputChanged: (stateKey: string, ev: React.FormEvent<HTMLInputElement>) => void;
+    onInputChanged: (stateKey: "email", ev: React.FormEvent<HTMLInputElement>) => void;
     onLoginClick: () => void;
     onSubmitForm: (ev: React.FormEvent) => void;
 }
diff --git a/src/components/views/dialogs/DeactivateAccountDialog.tsx b/src/components/views/dialogs/DeactivateAccountDialog.tsx
index d59f42109d..c53ff765f0 100644
--- a/src/components/views/dialogs/DeactivateAccountDialog.tsx
+++ b/src/components/views/dialogs/DeactivateAccountDialog.tsx
@@ -130,7 +130,7 @@ export default class DeactivateAccountDialog extends React.Component<IProps, ISt
         // but given that a deactivation is followed by a local logout and all object instances being thrown away
         // this isn't done.
         MatrixClientPeg.safeGet()
-            .deactivateAccount(auth, this.state.shouldErase)
+            .deactivateAccount(auth ?? undefined, this.state.shouldErase)
             .then((r) => {
                 // Deactivation worked - logout & close this dialog
                 defaultDispatcher.fire(Action.TriggerLogout);
@@ -163,7 +163,7 @@ export default class DeactivateAccountDialog extends React.Component<IProps, ISt
 
     private initAuth(shouldErase: boolean): void {
         MatrixClientPeg.safeGet()
-            .deactivateAccount(null, shouldErase)
+            .deactivateAccount(undefined, shouldErase)
             .then((r) => {
                 // If we got here, oops. The server didn't require any auth.
                 // Our application lifecycle will catch the error and do the logout bits.
diff --git a/src/components/views/dialogs/devtools/RoomState.tsx b/src/components/views/dialogs/devtools/RoomState.tsx
index 3c6ac3a935..b83d977248 100644
--- a/src/components/views/dialogs/devtools/RoomState.tsx
+++ b/src/components/views/dialogs/devtools/RoomState.tsx
@@ -37,7 +37,7 @@ export const StateEventEditor: React.FC<IEditorProps> = ({ mxEvent, onBack }) =>
         [mxEvent],
     );
 
-    const onSend = async ([eventType, stateKey]: string[], content?: IContent): Promise<void> => {
+    const onSend = async ([eventType, stateKey]: string[], content: IContent): Promise<void> => {
         await cli.sendStateEvent(context.room.roomId, eventType, content, stateKey);
     };
 
diff --git a/src/components/views/messages/DownloadActionButton.tsx b/src/components/views/messages/DownloadActionButton.tsx
index d1d416d7e3..8e974c1e15 100644
--- a/src/components/views/messages/DownloadActionButton.tsx
+++ b/src/components/views/messages/DownloadActionButton.tsx
@@ -31,7 +31,7 @@ interface IProps {
     // XXX: It can take a cycle or two for the MessageActionBar to have all the props/setup
     // required to get us a MediaEventHelper, so we use a getter function instead to prod for
     // one.
-    mediaEventHelperGet: () => MediaEventHelper;
+    mediaEventHelperGet: () => MediaEventHelper | undefined;
 }
 
 interface IState {
@@ -53,9 +53,10 @@ export default class DownloadActionButton extends React.PureComponent<IProps, IS
     }
 
     private onDownloadClick = async (): Promise<void> => {
-        if (this.state.loading) return;
+        const mediaEventHelper = this.props.mediaEventHelperGet();
+        if (this.state.loading || !mediaEventHelper) return;
 
-        if (this.props.mediaEventHelperGet().media.isEncrypted) {
+        if (mediaEventHelper.media.isEncrypted) {
             this.setState({ tooltip: _td("Decrypting") });
         }
 
@@ -66,7 +67,7 @@ export default class DownloadActionButton extends React.PureComponent<IProps, IS
             return this.doDownload(this.state.blob);
         }
 
-        const blob = await this.props.mediaEventHelperGet().sourceBlob.value;
+        const blob = await mediaEventHelper.sourceBlob.value;
         this.setState({ blob });
         await this.doDownload(blob);
     };
@@ -74,7 +75,7 @@ export default class DownloadActionButton extends React.PureComponent<IProps, IS
     private async doDownload(blob: Blob): Promise<void> {
         await this.downloader.download({
             blob,
-            name: this.props.mediaEventHelperGet().fileName,
+            name: this.props.mediaEventHelperGet()!.fileName,
         });
         this.setState({ loading: false });
     }
diff --git a/src/components/views/messages/MessageActionBar.tsx b/src/components/views/messages/MessageActionBar.tsx
index e792a47221..5bf600c02e 100644
--- a/src/components/views/messages/MessageActionBar.tsx
+++ b/src/components/views/messages/MessageActionBar.tsx
@@ -53,14 +53,13 @@ import { Key } from "../../../Keyboard";
 import { ALTERNATE_KEY_NAME } from "../../../accessibility/KeyboardShortcuts";
 import { Action } from "../../../dispatcher/actions";
 import { ShowThreadPayload } from "../../../dispatcher/payloads/ShowThreadPayload";
-import { GetRelationsForEvent } from "../rooms/EventTile";
+import { GetRelationsForEvent, IEventTileType } from "../rooms/EventTile";
 import { VoiceBroadcastInfoEventType } from "../../../voice-broadcast/types";
 import { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IOptionsButtonProps {
     mxEvent: MatrixEvent;
-    // TODO: Types
-    getTile: () => any | null;
+    getTile: () => IEventTileType | null;
     getReplyChain: () => ReplyChain | null;
     permalinkCreator?: RoomPermalinkCreator;
     onFocusChange: (menuDisplayed: boolean) => void;
@@ -97,7 +96,7 @@ const OptionsButton: React.FC<IOptionsButtonProps> = ({
 
     let contextMenu: ReactElement | undefined;
     if (menuDisplayed && button.current) {
-        const tile = getTile && getTile();
+        const tile = getTile?.();
         const replyChain = getReplyChain();
 
         const buttonRect = button.current.getBoundingClientRect();
@@ -254,8 +253,7 @@ const ReplyInThreadButton: React.FC<IReplyInThreadButton> = ({ mxEvent }) => {
 interface IMessageActionBarProps {
     mxEvent: MatrixEvent;
     reactions?: Relations | null | undefined;
-    // TODO: Types
-    getTile: () => any | null;
+    getTile: () => IEventTileType | null;
     getReplyChain: () => ReplyChain | null;
     permalinkCreator?: RoomPermalinkCreator;
     onFocusChange?: (menuDisplayed: boolean) => void;
@@ -487,7 +485,7 @@ export default class MessageActionBar extends React.PureComponent<IMessageAction
                         0,
                         <DownloadActionButton
                             mxEvent={this.props.mxEvent}
-                            mediaEventHelperGet={() => this.props.getTile?.().getMediaHelper?.()}
+                            mediaEventHelperGet={() => this.props.getTile()?.getMediaHelper?.()}
                             key="download"
                         />,
                     );
diff --git a/src/components/views/rooms/EventTile.tsx b/src/components/views/rooms/EventTile.tsx
index 17aa6f92a8..f750cd5510 100644
--- a/src/components/views/rooms/EventTile.tsx
+++ b/src/components/views/rooms/EventTile.tsx
@@ -107,6 +107,7 @@ export interface IEventTileOps {
 
 export interface IEventTileType extends React.Component {
     getEventTileOps?(): IEventTileOps;
+    getMediaHelper(): MediaEventHelper | undefined;
 }
 
 export interface EventTileProps {
diff --git a/src/components/views/settings/JoinRuleSettings.tsx b/src/components/views/settings/JoinRuleSettings.tsx
index 864529e6b2..4cdefc8e5c 100644
--- a/src/components/views/settings/JoinRuleSettings.tsx
+++ b/src/components/views/settings/JoinRuleSettings.tsx
@@ -61,7 +61,7 @@ const JoinRuleSettings: React.FC<JoinRuleSettingsProps> = ({
 
     const disabled = !room.currentState.mayClientSendStateEvent(EventType.RoomJoinRules, cli);
 
-    const [content, setContent] = useLocalEcho<IJoinRuleEventContent | undefined>(
+    const [content, setContent] = useLocalEcho<IJoinRuleEventContent | undefined, IJoinRuleEventContent>(
         () => room.currentState.getStateEvents(EventType.RoomJoinRules, "")?.getContent(),
         (content) => cli.sendStateEvent(room.roomId, EventType.RoomJoinRules, content, ""),
         onError,
diff --git a/src/hooks/useLocalEcho.ts b/src/hooks/useLocalEcho.ts
index e1374c82c5..6305d56088 100644
--- a/src/hooks/useLocalEcho.ts
+++ b/src/hooks/useLocalEcho.ts
@@ -16,13 +16,13 @@ limitations under the License.
 
 import { useState } from "react";
 
-export const useLocalEcho = <T>(
+export const useLocalEcho = <T, V extends T = T>(
     currentFactory: () => T,
-    setterFn: (value: T) => Promise<unknown>,
+    setterFn: (value: V) => Promise<unknown>,
     errorFn: (error: unknown) => void,
-): [value: T, handler: (value: T) => void] => {
+): [value: T, handler: (value: V) => void] => {
     const [value, setValue] = useState(currentFactory);
-    const handler = async (value: T): Promise<void> => {
+    const handler = async (value: V): Promise<void> => {
         setValue(value);
         try {
             await setterFn(value);
diff --git a/src/utils/dm/startDm.ts b/src/utils/dm/startDm.ts
index f3731e117d..b69f449ef6 100644
--- a/src/utils/dm/startDm.ts
+++ b/src/utils/dm/startDm.ts
@@ -25,7 +25,7 @@ import { isLocalRoom } from "../localRoom/isLocalRoom";
 import { findDMForUser } from "./findDMForUser";
 import dis from "../../dispatcher/dispatcher";
 import { getAddressType } from "../../UserAddress";
-import createRoom from "../../createRoom";
+import createRoom, { IOpts } from "../../createRoom";
 
 /**
  * Start a DM.
@@ -53,7 +53,7 @@ export async function startDm(client: MatrixClient, targets: Member[], showSpinn
         return Promise.resolve(existingRoom.roomId);
     }
 
-    const createRoomOptions = { inlineErrors: true } as any; // XXX: Type out `createRoomOptions`
+    const createRoomOptions: IOpts = { inlineErrors: true };
 
     if (await determineCreateRoomEncryptionOption(client, targets)) {
         createRoomOptions.encryption = true;