Update docs/faq.md: update description related to installation on matrix.example.com

Summary:
- Copy a paragraph from docs/howto-server-delegation.md
- Simplify instruction to install on matrix.example.com by removing repetitive description
- Remove duplicated description about server delegation
- Replace deprecated (or soon to be deprecated) services on configuration example for inventory/host_vars/matrix.example.com/vars.yml

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/faq.md

@@ -234,9 +234,9 @@ It's the same with email servers. Your email address is likely `name@company.com
 
 Using a separate domain name is easier to manage (although it's a little hard to get right at first) and keeps your Matrix server isolated from your website (if you have one), from your email server (if you have one), etc.
 
-We allow `matrix.example.com` to be the Matrix server handling Matrix stuff for `example.com` by [Server Delegation](howto-server-delegation.md). During the installation procedure, we recommend that you set up server delegation using the [.well-known](configuring-well-known.md) method.
+By default, this playbook sets up services on your Matrix server (`matrix.example.com`). To have this server officially be responsible for Matrix services for the base domain (`example.com`), you need to set up [Server Delegation](howto-server-delegation.md). This is normally done by [configuring well-known](configuring-well-known.md) files on the base domain.
 
-If you'd really like to install Matrix services directly on the base domain, see [How do I install on matrix.example.com without involving the base domain?](#how-do-i-install-on-matrixexamplecom-without-involving-the-base-domain)
+If you'd really like to install Matrix services directly on the base domain (or need to do so), see [How do I install on matrix.example.com without involving the base domain?](#how-do-i-install-on-matrixexamplecom-without-involving-the-base-domain)
 
 ### I don't control anything on the base domain and can't set up delegation to matrix.example.com. What do I do?
 
@@ -248,11 +248,7 @@ If you really can't obtain an HTTPS certificate for your base domain, you can ta
 
 ### How do I install on matrix.example.com without involving the base domain?
 
-This Ansible playbook guides you into installing a server for `example.com` (user identifiers are like this: `@user:example.com`), while the server is at `matrix.example.com`.
-
-We allow `matrix.example.com` to be the Matrix server handling Matrix stuff for `example.com` by [Server Delegation](howto-server-delegation.md). During the installation procedure, we recommend that you set up server delegation using the [.well-known](configuring-well-known.md) method.
-
-If you're fine with uglier identifiers (`@user:matrix.example.com`, which is the equivalent of having an email address like `bob@mail.company.com`, instead of just `bob@company.com`), you can do that as well using the following configuration in your `vars.yml` file:
+Add the following configuration to your `inventory/host_vars/matrix.example.com/vars.yml` file:
 
 ```yaml
 # This is what your identifiers are like (e.g. `@bob:matrix.example.com`).
@@ -267,17 +263,20 @@ matrix_server_fqn_matrix: "matrix.example.com"
 # Feel free to use `element.matrix.example.com`, if you'd prefer that.
 matrix_server_fqn_element: "element.example.com"
 
-# This is where you access Dimension (if enabled via `matrix_dimension_enabled: true`; NOT enabled by default).
+# This is where you access Etherpad (if enabled via `etherpad_enabled: true`; NOT enabled by default).
 #
-# Feel free to use `dimension.matrix.example.com`, if you'd prefer that.
-matrix_server_fqn_dimension: "dimension.example.com"
+# Feel free to use `etherpad.matrix.example.com`, if you'd prefer that.
+matrix_server_fqn_etherpad: "etherpad.example.com"
+```
 
-# This is where you access Jitsi (if enabled via `jitsi_enabled: true`; NOT enabled by default).
-#
-# Feel free to use `jitsi.matrix.example.com`, if you'd prefer that.
-matrix_server_fqn_jitsi: "jitsi.example.com"
+After configuring the playbook, run the [installation](installing.md) command:
+
+```
+ansible-playbook -i inventory/hosts setup.yml --tags=setup-all,start
 ```
 
+**Note**: without setting up [server delegation](howto-server-delegation.md) to `matrix.example.com`, your user identifiers will be like `@user:matrix.example.com`. This is equivalent to having an email address like `bob@mail.company.com`, instead of just `bob@company.com`.
+
 ### I don't use the base domain for anything. How am I supposed to set up Server Delegation for Matrix services?
 
 If you don't use your base domain for anything, then it's hard for you to "serve files over HTTPS" on it -- something we ask you to do for the [.well-known](configuring-well-known.md) setup (needed for [Server Delegation](howto-server-delegation.md)).