diff --git a/changelog.d/14778.doc b/changelog.d/14778.doc
new file mode 100644
index 0000000000..677f999f8d
--- /dev/null
+++ b/changelog.d/14778.doc
@@ -0,0 +1 @@
+Document using Twitter as a OAuth 2.0 authentication provider.
diff --git a/docs/openid.md b/docs/openid.md
index e4ad45f306..45aa24dd24 100644
--- a/docs/openid.md
+++ b/docs/openid.md
@@ -88,98 +88,41 @@ oidc_providers:
         display_name_template: "{{ user.name }}"
 ```
 
-### Dex
+### Apple
 
-[Dex][dex-idp] is a simple, open-source OpenID Connect Provider.
-Although it is designed to help building a full-blown provider with an
-external database, it can be configured with static passwords in a config file.
+Configuring "Sign in with Apple" (SiWA) requires an Apple Developer account.
 
-Follow the [Getting Started guide](https://dexidp.io/docs/getting-started/)
-to install Dex.
+You will need to create a new "Services ID" for SiWA, and create and download a
+private key with "SiWA" enabled.
 
-Edit `examples/config-dev.yaml` config file from the Dex repo to add a client:
+As well as the private key file, you will need:
+ * Client ID: the "identifier" you gave the "Services ID"
+ * Team ID: a 10-character ID associated with your developer account.
+ * Key ID: the 10-character identifier for the key.
+
+[Apple's developer documentation](https://help.apple.com/developer-account/?lang=en#/dev77c875b7e)
+has more information on setting up SiWA.
+
+The synapse config will look like this:
 
 ```yaml
-staticClients:
-- id: synapse
-  secret: secret
-  redirectURIs:
-  - '[synapse public baseurl]/_synapse/client/oidc/callback'
-  name: 'Synapse'
-```
-
-Run with `dex serve examples/config-dev.yaml`.
-
-Synapse config:
-
-```yaml
-oidc_providers:
-  - idp_id: dex
-    idp_name: "My Dex server"
-    skip_verification: true # This is needed as Dex is served on an insecure endpoint
-    issuer: "http://127.0.0.1:5556/dex"
-    client_id: "synapse"
-    client_secret: "secret"
-    scopes: ["openid", "profile"]
+  - idp_id: apple
+    idp_name: Apple
+    issuer: "https://appleid.apple.com"
+    client_id: "your-client-id" # Set to the "identifier" for your "ServicesID"
+    client_auth_method: "client_secret_post"
+    client_secret_jwt_key:
+      key_file: "/path/to/AuthKey_KEYIDCODE.p8"  # point to your key file
+      jwt_header:
+        alg: ES256
+        kid: "KEYIDCODE"   # Set to the 10-char Key ID
+      jwt_payload:
+        iss: TEAMIDCODE    # Set to the 10-char Team ID
+    scopes: ["name", "email", "openid"]
+    authorization_endpoint: https://appleid.apple.com/auth/authorize?response_mode=form_post
     user_mapping_provider:
       config:
-        localpart_template: "{{ user.name }}"
-        display_name_template: "{{ user.name|capitalize }}"
-```
-### Keycloak
-
-[Keycloak][keycloak-idp] is an opensource IdP maintained by Red Hat.
-
-Keycloak supports OIDC Back-Channel Logout, which sends logout notification to Synapse, so that Synapse users get logged out when they log out from Keycloak.
-This can be optionally enabled by setting `backchannel_logout_enabled` to `true` in the Synapse configuration, and by setting the "Backchannel Logout URL" in Keycloak.
-
-Follow the [Getting Started Guide](https://www.keycloak.org/getting-started) to install Keycloak and set up a realm.
-
-1. Click `Clients` in the sidebar and click `Create`
-
-2. Fill in the fields as below:
-
-| Field | Value |
-|-----------|-----------|
-| Client ID | `synapse` |
-| Client Protocol | `openid-connect` |
-
-3. Click `Save`
-4. Fill in the fields as below:
-
-| Field | Value |
-|-----------|-----------|
-| Client ID | `synapse` |
-| Enabled | `On` |
-| Client Protocol | `openid-connect` |
-| Access Type | `confidential` |
-| Valid Redirect URIs | `[synapse public baseurl]/_synapse/client/oidc/callback` |
-| Backchannel Logout URL (optional) | `[synapse public baseurl]/_synapse/client/oidc/backchannel_logout` |
-| Backchannel Logout Session Required (optional) | `On` |
-
-5. Click `Save`
-6. On the Credentials tab, update the fields:
-
-| Field | Value |
-|-------|-------|
-| Client Authenticator | `Client ID and Secret` |
-
-7. Click `Regenerate Secret`
-8. Copy Secret
-
-```yaml
-oidc_providers:
-  - idp_id: keycloak
-    idp_name: "My KeyCloak server"
-    issuer: "https://127.0.0.1:8443/realms/{realm_name}"
-    client_id: "synapse"
-    client_secret: "copy secret generated from above"
-    scopes: ["openid", "profile"]
-    user_mapping_provider:
-      config:
-        localpart_template: "{{ user.preferred_username }}"
-        display_name_template: "{{ user.name }}"
-    backchannel_logout_enabled: true # Optional
+        email_template: "{{ user.email }}"
 ```
 
 ### Auth0
@@ -262,285 +205,43 @@ oidc_providers:
         display_name_template: "{{ user.preferred_username|capitalize }}" # TO BE FILLED: If your users have names in Authentik and you want those in Synapse, this should be replaced with user.name|capitalize.
 ```
 
-### LemonLDAP
+### Dex
 
-[LemonLDAP::NG][lemonldap] is an open-source IdP solution.
+[Dex][dex-idp] is a simple, open-source OpenID Connect Provider.
+Although it is designed to help building a full-blown provider with an
+external database, it can be configured with static passwords in a config file.
 
-1. Create an OpenID Connect Relying Parties in LemonLDAP::NG
-2. The parameters are:
-- Client ID under the basic menu of the new Relying Parties (`Options > Basic >
-  Client ID`)
-- Client secret (`Options > Basic > Client secret`)
-- JWT Algorithm: RS256 within the security menu of the new Relying Parties
-  (`Options > Security > ID Token signature algorithm` and `Options > Security >
-  Access Token signature algorithm`)
-- Scopes: OpenID, Email and Profile
-- Allowed redirection addresses for login (`Options > Basic > Allowed
-  redirection addresses for login` ) :
-  `[synapse public baseurl]/_synapse/client/oidc/callback`
+Follow the [Getting Started guide](https://dexidp.io/docs/getting-started/)
+to install Dex.
+
+Edit `examples/config-dev.yaml` config file from the Dex repo to add a client:
 
-Synapse config:
 ```yaml
-oidc_providers:
-  - idp_id: lemonldap
-    idp_name: lemonldap
-    discover: true
-    issuer: "https://auth.example.org/" # TO BE FILLED: replace with your domain
-    client_id: "your client id" # TO BE FILLED
-    client_secret: "your client secret" # TO BE FILLED
-    scopes:
-      - "openid"
-      - "profile"
-      - "email"
-    user_mapping_provider:
-      config:
-        localpart_template: "{{ user.preferred_username }}}"
-        # TO BE FILLED: If your users have names in LemonLDAP::NG and you want those in Synapse, this should be replaced with user.name|capitalize or any valid filter.
-        display_name_template: "{{ user.preferred_username|capitalize }}"
+staticClients:
+- id: synapse
+  secret: secret
+  redirectURIs:
+  - '[synapse public baseurl]/_synapse/client/oidc/callback'
+  name: 'Synapse'
 ```
 
-### GitHub
-
-[GitHub][github-idp] is a bit special as it is not an OpenID Connect compliant provider, but
-just a regular OAuth2 provider.
-
-The [`/user` API endpoint](https://developer.github.com/v3/users/#get-the-authenticated-user)
-can be used to retrieve information on the authenticated user. As the Synapse
-login mechanism needs an attribute to uniquely identify users, and that endpoint
-does not return a `sub` property, an alternative `subject_claim` has to be set.
-
-1. Create a new OAuth application: [https://github.com/settings/applications/new](https://github.com/settings/applications/new).
-2. Set the callback URL to `[synapse public baseurl]/_synapse/client/oidc/callback`.
+Run with `dex serve examples/config-dev.yaml`.
 
 Synapse config:
 
 ```yaml
 oidc_providers:
-  - idp_id: github
-    idp_name: Github
-    idp_brand: "github"  # optional: styling hint for clients
-    discover: false
-    issuer: "https://github.com/"
-    client_id: "your-client-id" # TO BE FILLED
-    client_secret: "your-client-secret" # TO BE FILLED
-    authorization_endpoint: "https://github.com/login/oauth/authorize"
-    token_endpoint: "https://github.com/login/oauth/access_token"
-    userinfo_endpoint: "https://api.github.com/user"
-    scopes: ["read:user"]
-    user_mapping_provider:
-      config:
-        subject_claim: "id"
-        localpart_template: "{{ user.login }}"
-        display_name_template: "{{ user.name }}"
-```
-
-### Google
-
-[Google][google-idp] is an OpenID certified authentication and authorisation provider.
-
-1. Set up a project in the Google API Console (see 
-   [documentation](https://developers.google.com/identity/protocols/oauth2/openid-connect#appsetup)).
-3. Add an "OAuth Client ID" for a Web Application under "Credentials".
-4. Copy the Client ID and Client Secret, and add the following to your synapse config:
-   ```yaml
-   oidc_providers:
-     - idp_id: google
-       idp_name: Google
-       idp_brand: "google"  # optional: styling hint for clients
-       issuer: "https://accounts.google.com/"
-       client_id: "your-client-id" # TO BE FILLED
-       client_secret: "your-client-secret" # TO BE FILLED
-       scopes: ["openid", "profile", "email"] # email is optional, read below
-       user_mapping_provider:
-         config:
-           localpart_template: "{{ user.given_name|lower }}"
-           display_name_template: "{{ user.name }}"
-           email_template: "{{ user.email }}" # needs "email" in scopes above
-   ```
-4. Back in the Google console, add this Authorized redirect URI: `[synapse
-   public baseurl]/_synapse/client/oidc/callback`.
-
-### Twitch
-
-1. Setup a developer account on [Twitch](https://dev.twitch.tv/)
-2. Obtain the OAuth 2.0 credentials by [creating an app](https://dev.twitch.tv/console/apps/)
-3. Add this OAuth Redirect URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
-
-Synapse config:
-
-```yaml
-oidc_providers:
-  - idp_id: twitch
-    idp_name: Twitch
-    issuer: "https://id.twitch.tv/oauth2/"
-    client_id: "your-client-id" # TO BE FILLED
-    client_secret: "your-client-secret" # TO BE FILLED
-    client_auth_method: "client_secret_post"
-    user_mapping_provider:
-      config:
-        localpart_template: "{{ user.preferred_username }}"
-        display_name_template: "{{ user.name }}"
-```
-
-### GitLab
-
-1. Create a [new application](https://gitlab.com/profile/applications).
-2. Add the `read_user` and `openid` scopes.
-3. Add this Callback URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
-
-Synapse config:
-
-```yaml
-oidc_providers:
-  - idp_id: gitlab
-    idp_name: Gitlab
-    idp_brand: "gitlab"  # optional: styling hint for clients
-    issuer: "https://gitlab.com/"
-    client_id: "your-client-id" # TO BE FILLED
-    client_secret: "your-client-secret" # TO BE FILLED
-    client_auth_method: "client_secret_post"
-    scopes: ["openid", "read_user"]
-    user_profile_method: "userinfo_endpoint"
-    user_mapping_provider:
-      config:
-        localpart_template: '{{ user.nickname }}'
-        display_name_template: '{{ user.name }}'
-```
-
-### Facebook
-
-0. You will need a Facebook developer account. You can register for one
-   [here](https://developers.facebook.com/async/registration/).
-1. On the [apps](https://developers.facebook.com/apps/) page of the developer
-   console, "Create App", and choose "Build Connected Experiences".
-2. Once the app is created, add "Facebook Login" and choose "Web". You don't
-   need to go through the whole form here.
-3. In the left-hand menu, open "Products"/"Facebook Login"/"Settings".
-   * Add `[synapse public baseurl]/_synapse/client/oidc/callback` as an OAuth Redirect
-     URL.
-4. In the left-hand menu, open "Settings/Basic". Here you can copy the "App ID"
-   and "App Secret" for use below.
-
-Synapse config:
-
-```yaml
-  - idp_id: facebook
-    idp_name: Facebook
-    idp_brand: "facebook"  # optional: styling hint for clients
-    discover: false
-    issuer: "https://www.facebook.com"
-    client_id: "your-client-id" # TO BE FILLED
-    client_secret: "your-client-secret" # TO BE FILLED
-    scopes: ["openid", "email"]
-    authorization_endpoint: "https://facebook.com/dialog/oauth"
-    token_endpoint: "https://graph.facebook.com/v9.0/oauth/access_token"
-    jwks_uri: "https://www.facebook.com/.well-known/oauth/openid/jwks/"
-    user_mapping_provider:
-      config:
-        display_name_template: "{{ user.name }}"
-        email_template: "{{ user.email }}"
-```
-
-Relevant documents:
- * [Manually Build a Login Flow](https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow)
- * [Using Facebook's Graph API](https://developers.facebook.com/docs/graph-api/using-graph-api/)
- * [Reference to the User endpoint](https://developers.facebook.com/docs/graph-api/reference/user)
-
-Facebook do have an [OIDC discovery endpoint](https://www.facebook.com/.well-known/openid-configuration),
-but it has a `response_types_supported` which excludes "code" (which we rely on, and
-is even mentioned in their [documentation](https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow#login)),
-so we have to disable discovery and configure the URIs manually.
-
-### Gitea
-
-Gitea is, like Github, not an OpenID provider, but just an OAuth2 provider.
-
-The [`/user` API endpoint](https://try.gitea.io/api/swagger#/user/userGetCurrent)
-can be used to retrieve information on the authenticated user. As the Synapse
-login mechanism needs an attribute to uniquely identify users, and that endpoint
-does not return a `sub` property, an alternative `subject_claim` has to be set.
-
-1. Create a new application.
-2. Add this Callback URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
-
-Synapse config:
-
-```yaml
-oidc_providers:
-  - idp_id: gitea
-    idp_name: Gitea
-    discover: false
-    issuer: "https://your-gitea.com/"
-    client_id: "your-client-id" # TO BE FILLED
-    client_secret: "your-client-secret" # TO BE FILLED
-    client_auth_method: client_secret_post
-    scopes: [] # Gitea doesn't support Scopes
-    authorization_endpoint: "https://your-gitea.com/login/oauth/authorize"
-    token_endpoint: "https://your-gitea.com/login/oauth/access_token"
-    userinfo_endpoint: "https://your-gitea.com/api/v1/user"
-    user_mapping_provider:
-      config:
-        subject_claim: "id"
-        localpart_template: "{{ user.login }}"
-        display_name_template: "{{ user.full_name }}"
-```
-
-### XWiki
-
-Install [OpenID Connect Provider](https://extensions.xwiki.org/xwiki/bin/view/Extension/OpenID%20Connect/OpenID%20Connect%20Provider/) extension in your [XWiki](https://www.xwiki.org) instance.
-
-Synapse config:
-
-```yaml
-oidc_providers:
-  - idp_id: xwiki
-    idp_name: "XWiki"
-    issuer: "https://myxwikihost/xwiki/oidc/"
-    client_id: "your-client-id" # TO BE FILLED
-    client_auth_method: none
+  - idp_id: dex
+    idp_name: "My Dex server"
+    skip_verification: true # This is needed as Dex is served on an insecure endpoint
+    issuer: "http://127.0.0.1:5556/dex"
+    client_id: "synapse"
+    client_secret: "secret"
     scopes: ["openid", "profile"]
-    user_profile_method: "userinfo_endpoint"
     user_mapping_provider:
       config:
-        localpart_template: "{{ user.preferred_username }}"
-        display_name_template: "{{ user.name }}"
-```
-
-### Apple
-
-Configuring "Sign in with Apple" (SiWA) requires an Apple Developer account.
-
-You will need to create a new "Services ID" for SiWA, and create and download a
-private key with "SiWA" enabled.
-
-As well as the private key file, you will need:
- * Client ID: the "identifier" you gave the "Services ID"
- * Team ID: a 10-character ID associated with your developer account.
- * Key ID: the 10-character identifier for the key.
-
-[Apple's developer documentation](https://help.apple.com/developer-account/?lang=en#/dev77c875b7e)
-has more information on setting up SiWA.
-
-The synapse config will look like this:
-
-```yaml
-  - idp_id: apple
-    idp_name: Apple
-    issuer: "https://appleid.apple.com"
-    client_id: "your-client-id" # Set to the "identifier" for your "ServicesID"
-    client_auth_method: "client_secret_post"
-    client_secret_jwt_key:
-      key_file: "/path/to/AuthKey_KEYIDCODE.p8"  # point to your key file
-      jwt_header:
-        alg: ES256
-        kid: "KEYIDCODE"   # Set to the 10-char Key ID
-      jwt_payload:
-        iss: TEAMIDCODE    # Set to the 10-char Team ID
-    scopes: ["name", "email", "openid"]
-    authorization_endpoint: https://appleid.apple.com/auth/authorize?response_mode=form_post
-    user_mapping_provider:
-      config:
-        email_template: "{{ user.email }}"
+        localpart_template: "{{ user.name }}"
+        display_name_template: "{{ user.name|capitalize }}"
 ```
 
 ### Django OAuth Toolkit
@@ -591,6 +292,263 @@ oidc_providers:
         email_template: "{{ user.email }}"
 ```
 
+### Facebook
+
+0. You will need a Facebook developer account. You can register for one
+   [here](https://developers.facebook.com/async/registration/).
+1. On the [apps](https://developers.facebook.com/apps/) page of the developer
+   console, "Create App", and choose "Build Connected Experiences".
+2. Once the app is created, add "Facebook Login" and choose "Web". You don't
+   need to go through the whole form here.
+3. In the left-hand menu, open "Products"/"Facebook Login"/"Settings".
+   * Add `[synapse public baseurl]/_synapse/client/oidc/callback` as an OAuth Redirect
+     URL.
+4. In the left-hand menu, open "Settings/Basic". Here you can copy the "App ID"
+   and "App Secret" for use below.
+
+Synapse config:
+
+```yaml
+  - idp_id: facebook
+    idp_name: Facebook
+    idp_brand: "facebook"  # optional: styling hint for clients
+    discover: false
+    issuer: "https://www.facebook.com"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    scopes: ["openid", "email"]
+    authorization_endpoint: "https://facebook.com/dialog/oauth"
+    token_endpoint: "https://graph.facebook.com/v9.0/oauth/access_token"
+    jwks_uri: "https://www.facebook.com/.well-known/oauth/openid/jwks/"
+    user_mapping_provider:
+      config:
+        display_name_template: "{{ user.name }}"
+        email_template: "{{ user.email }}"
+```
+
+Relevant documents:
+ * [Manually Build a Login Flow](https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow)
+ * [Using Facebook's Graph API](https://developers.facebook.com/docs/graph-api/using-graph-api/)
+ * [Reference to the User endpoint](https://developers.facebook.com/docs/graph-api/reference/user)
+
+Facebook do have an [OIDC discovery endpoint](https://www.facebook.com/.well-known/openid-configuration),
+but it has a `response_types_supported` which excludes "code" (which we rely on, and
+is even mentioned in their [documentation](https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow#login)),
+so we have to disable discovery and configure the URIs manually.
+
+### GitHub
+
+[GitHub][github-idp] is a bit special as it is not an OpenID Connect compliant provider, but
+just a regular OAuth2 provider.
+
+The [`/user` API endpoint](https://developer.github.com/v3/users/#get-the-authenticated-user)
+can be used to retrieve information on the authenticated user. As the Synapse
+login mechanism needs an attribute to uniquely identify users, and that endpoint
+does not return a `sub` property, an alternative `subject_claim` has to be set.
+
+1. Create a new OAuth application: [https://github.com/settings/applications/new](https://github.com/settings/applications/new).
+2. Set the callback URL to `[synapse public baseurl]/_synapse/client/oidc/callback`.
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: github
+    idp_name: Github
+    idp_brand: "github"  # optional: styling hint for clients
+    discover: false
+    issuer: "https://github.com/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    authorization_endpoint: "https://github.com/login/oauth/authorize"
+    token_endpoint: "https://github.com/login/oauth/access_token"
+    userinfo_endpoint: "https://api.github.com/user"
+    scopes: ["read:user"]
+    user_mapping_provider:
+      config:
+        subject_claim: "id"
+        localpart_template: "{{ user.login }}"
+        display_name_template: "{{ user.name }}"
+```
+
+### GitLab
+
+1. Create a [new application](https://gitlab.com/profile/applications).
+2. Add the `read_user` and `openid` scopes.
+3. Add this Callback URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: gitlab
+    idp_name: Gitlab
+    idp_brand: "gitlab"  # optional: styling hint for clients
+    issuer: "https://gitlab.com/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    client_auth_method: "client_secret_post"
+    scopes: ["openid", "read_user"]
+    user_profile_method: "userinfo_endpoint"
+    user_mapping_provider:
+      config:
+        localpart_template: '{{ user.nickname }}'
+        display_name_template: '{{ user.name }}'
+```
+
+### Gitea
+
+Gitea is, like Github, not an OpenID provider, but just an OAuth2 provider.
+
+The [`/user` API endpoint](https://try.gitea.io/api/swagger#/user/userGetCurrent)
+can be used to retrieve information on the authenticated user. As the Synapse
+login mechanism needs an attribute to uniquely identify users, and that endpoint
+does not return a `sub` property, an alternative `subject_claim` has to be set.
+
+1. Create a new application.
+2. Add this Callback URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: gitea
+    idp_name: Gitea
+    discover: false
+    issuer: "https://your-gitea.com/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    client_auth_method: client_secret_post
+    scopes: [] # Gitea doesn't support Scopes
+    authorization_endpoint: "https://your-gitea.com/login/oauth/authorize"
+    token_endpoint: "https://your-gitea.com/login/oauth/access_token"
+    userinfo_endpoint: "https://your-gitea.com/api/v1/user"
+    user_mapping_provider:
+      config:
+        subject_claim: "id"
+        localpart_template: "{{ user.login }}"
+        display_name_template: "{{ user.full_name }}"
+```
+
+### Google
+
+[Google][google-idp] is an OpenID certified authentication and authorisation provider.
+
+1. Set up a project in the Google API Console (see 
+   [documentation](https://developers.google.com/identity/protocols/oauth2/openid-connect#appsetup)).
+3. Add an "OAuth Client ID" for a Web Application under "Credentials".
+4. Copy the Client ID and Client Secret, and add the following to your synapse config:
+   ```yaml
+   oidc_providers:
+     - idp_id: google
+       idp_name: Google
+       idp_brand: "google"  # optional: styling hint for clients
+       issuer: "https://accounts.google.com/"
+       client_id: "your-client-id" # TO BE FILLED
+       client_secret: "your-client-secret" # TO BE FILLED
+       scopes: ["openid", "profile", "email"] # email is optional, read below
+       user_mapping_provider:
+         config:
+           localpart_template: "{{ user.given_name|lower }}"
+           display_name_template: "{{ user.name }}"
+           email_template: "{{ user.email }}" # needs "email" in scopes above
+   ```
+4. Back in the Google console, add this Authorized redirect URI: `[synapse
+   public baseurl]/_synapse/client/oidc/callback`.
+
+### Keycloak
+
+[Keycloak][keycloak-idp] is an opensource IdP maintained by Red Hat.
+
+Keycloak supports OIDC Back-Channel Logout, which sends logout notification to Synapse, so that Synapse users get logged out when they log out from Keycloak.
+This can be optionally enabled by setting `backchannel_logout_enabled` to `true` in the Synapse configuration, and by setting the "Backchannel Logout URL" in Keycloak.
+
+Follow the [Getting Started Guide](https://www.keycloak.org/getting-started) to install Keycloak and set up a realm.
+
+1. Click `Clients` in the sidebar and click `Create`
+
+2. Fill in the fields as below:
+
+| Field | Value |
+|-----------|-----------|
+| Client ID | `synapse` |
+| Client Protocol | `openid-connect` |
+
+3. Click `Save`
+4. Fill in the fields as below:
+
+| Field | Value |
+|-----------|-----------|
+| Client ID | `synapse` |
+| Enabled | `On` |
+| Client Protocol | `openid-connect` |
+| Access Type | `confidential` |
+| Valid Redirect URIs | `[synapse public baseurl]/_synapse/client/oidc/callback` |
+| Backchannel Logout URL (optional) | `[synapse public baseurl]/_synapse/client/oidc/backchannel_logout` |
+| Backchannel Logout Session Required (optional) | `On` |
+
+5. Click `Save`
+6. On the Credentials tab, update the fields:
+
+| Field | Value |
+|-------|-------|
+| Client Authenticator | `Client ID and Secret` |
+
+7. Click `Regenerate Secret`
+8. Copy Secret
+
+```yaml
+oidc_providers:
+  - idp_id: keycloak
+    idp_name: "My KeyCloak server"
+    issuer: "https://127.0.0.1:8443/realms/{realm_name}"
+    client_id: "synapse"
+    client_secret: "copy secret generated from above"
+    scopes: ["openid", "profile"]
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ user.preferred_username }}"
+        display_name_template: "{{ user.name }}"
+    backchannel_logout_enabled: true # Optional
+```
+
+### LemonLDAP
+
+[LemonLDAP::NG][lemonldap] is an open-source IdP solution.
+
+1. Create an OpenID Connect Relying Parties in LemonLDAP::NG
+2. The parameters are:
+- Client ID under the basic menu of the new Relying Parties (`Options > Basic >
+  Client ID`)
+- Client secret (`Options > Basic > Client secret`)
+- JWT Algorithm: RS256 within the security menu of the new Relying Parties
+  (`Options > Security > ID Token signature algorithm` and `Options > Security >
+  Access Token signature algorithm`)
+- Scopes: OpenID, Email and Profile
+- Allowed redirection addresses for login (`Options > Basic > Allowed
+  redirection addresses for login` ) :
+  `[synapse public baseurl]/_synapse/client/oidc/callback`
+
+Synapse config:
+```yaml
+oidc_providers:
+  - idp_id: lemonldap
+    idp_name: lemonldap
+    discover: true
+    issuer: "https://auth.example.org/" # TO BE FILLED: replace with your domain
+    client_id: "your client id" # TO BE FILLED
+    client_secret: "your client secret" # TO BE FILLED
+    scopes:
+      - "openid"
+      - "profile"
+      - "email"
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ user.preferred_username }}}"
+        # TO BE FILLED: If your users have names in LemonLDAP::NG and you want those in Synapse, this should be replaced with user.name|capitalize or any valid filter.
+        display_name_template: "{{ user.preferred_username|capitalize }}"
+```
+
 ### Mastodon
 
 [Mastodon](https://docs.joinmastodon.org/) instances provide an [OAuth API](https://docs.joinmastodon.org/spec/oauth/), allowing those instances to be used as a single sign-on provider for Synapse.
@@ -631,3 +589,81 @@ oidc_providers:
 ```
 
 Note that the fields `client_id` and `client_secret` are taken from the CURL response above.
+
+### Twitch
+
+1. Setup a developer account on [Twitch](https://dev.twitch.tv/)
+2. Obtain the OAuth 2.0 credentials by [creating an app](https://dev.twitch.tv/console/apps/)
+3. Add this OAuth Redirect URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: twitch
+    idp_name: Twitch
+    issuer: "https://id.twitch.tv/oauth2/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    client_auth_method: "client_secret_post"
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ user.preferred_username }}"
+        display_name_template: "{{ user.name }}"
+```
+
+### Twitter
+
+*Using Twitter as an identity provider requires using Synapse 1.75.0 or later.*
+
+1. Setup a developer account on [Twitter](https://developer.twitter.com/en/portal/dashboard)
+2. Create a project & app.
+3. Enable user authentication and under "Type of App" choose "Web App, Automated App or Bot".
+4. Under "App info" set the callback URL to `[synapse public baseurl]/_synapse/client/oidc/callback`.
+5. Obtain the OAuth 2.0 credentials under the "Keys and tokens" tab, copy the "OAuth 2.0 Client ID and Client Secret"
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: twitter
+    idp_name: Twitter
+    idp_brand: "twitter"  # optional: styling hint for clients
+    discover: false  # Twitter is not OpenID compliant.
+    issuer: "https://twitter.com/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    pkce_method: "always"
+    # offline.access providers refresh tokens, tweet.read and users.read needed for userinfo request.
+    scopes: ["offline.access", "tweet.read", "users.read"]
+    authorization_endpoint: https://twitter.com/i/oauth2/authorize
+    token_endpoint: https://api.twitter.com/2/oauth2/token
+    userinfo_endpoint: https://api.twitter.com/2/users/me?user.fields=profile_image_url
+    user_mapping_provider:
+      config:
+        subject_template: "{{ user.data.id }}"
+        localpart_template: "{{ user.data.username }}"
+        display_name_template: "{{ user.data.name }}"
+        picture_template: "{{ user.data.profile_image_url }}"
+```
+
+### XWiki
+
+Install [OpenID Connect Provider](https://extensions.xwiki.org/xwiki/bin/view/Extension/OpenID%20Connect/OpenID%20Connect%20Provider/) extension in your [XWiki](https://www.xwiki.org) instance.
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: xwiki
+    idp_name: "XWiki"
+    issuer: "https://myxwikihost/xwiki/oidc/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_auth_method: none
+    scopes: ["openid", "profile"]
+    user_profile_method: "userinfo_endpoint"
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ user.preferred_username }}"
+        display_name_template: "{{ user.name }}"
+```