docs: Elaborate on issue reporting

We currently just link to the issue tracker without providing
any further guidance.

Improve on that by pointing to the appropriate handbook chapter,
point out extensions as a possible source of issues, and direct
users towards discourse/matrix for support/discussions.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3122>

README.md

@@ -6,8 +6,6 @@ advantage of the capabilities of modern graphics hardware and introduces
 innovative user interface concepts to provide a visually attractive and
 easy to use experience.
 
-Bugs should be reported to the GNOME [bug tracking system][bug-tracker].
-
 All interactions with the project should follow the [Code of Conduct][conduct].
 
 [conduct]: https://conduct.gnome.org/
@@ -24,6 +22,35 @@ Please refer to the [schedule] to see when a new version will be released.
 
 [schedule]: https://release.gnome.org/calendar
 
+## Reporting bugs
+
+Bugs should be reported to the [issue tracking system][bug-tracker].
+
+The [GNOME handbook][bug-handbook] has useful information for creating
+effective issue reports.
+
+If you are using extensions, please confirm that an issue still happens
+without extensions. To properly disable extensions you can use the
+[extensions-app] and then restart your session. Disabling extensions
+without a restart is not sufficient to rule out extensions as the
+cause of a bug. If an issue can only be reproduced with a certain
+extension, please file an issue report against that extension first.
+
+Please note that the issue tracker is meant to be used for
+actionable issues only.
+
+For support questions, feedback on changes or general discussions,
+you can use:
+
+ - the [#gnome-shell matrix room][matrix-room]
+ - the `Desktop` category or `shell` tag on [GNOME Discourse][discourse]
+
+[bug-tracker]: https://gitlab.gnome.org/GNOME/gnome-shell/issues
+[bug-handbook]: https://handbook.gnome.org/issues/reporting.html
+[extensions-app]: https://apps.gnome.org/Extensions
+[matrix-room]: https://matrix.to/#/#gnome-shell:gnome.org
+[discourse]: https://discourse.gnome.org
+
 ## Contributing
 
 To contribute, open merge requests at https://gitlab.gnome.org/GNOME/gnome-shell.
@@ -37,5 +64,4 @@ Commit messages should follow the [commit message guidelines][commit-messages].
 GNOME Shell is distributed under the terms of the GNU General Public License,
 version 2 or later. See the [COPYING][license] file for details.
 
-[bug-tracker]: https://gitlab.gnome.org/GNOME/gnome-shell/issues
 [license]: COPYING