Point to the discussion forum as the main community entry point

Slack should no longer be used for asking for help. Instead, people
should head to the discussion forums at https://discuss.openedx.com.

CONTRIBUTING.rst

@@ -41,6 +41,24 @@ pull request.
 .. _start a discussion on JIRA: https://openedx.atlassian.net/secure/Dashboard.jspa
 .. _create a free JIRA account: https://openedx.atlassian.net/admin/users/sign-up
 
+.. _forum:
+
+Discussion forum
+----------------
+
+To ask technical questions and chat with the community, do not hesitate to join the
+`Open edX discussion forum <https://discuss.openedx.org/>`__. There are different
+categories for different topics:
+
+- `Devops <https://discuss.openedx.org/c/devops>`__ for installation help
+- `Development <https://discuss.openedx.org/c/development>`__, where Open edX developers
+  unite
+- `Community <https://discuss.openedx.org/c/community>`__ to discuss organizational
+  matters in the open source community
+- `Announcements <https://discuss.openedx.org/c/announcements>`__ where official Open edX
+  announcement are made
+- `Educators <https://discuss.openedx.org/c/educators>`__, to discuss online learning in general
+
 Slack
 -----
 
@@ -51,12 +69,14 @@ between 13:00 and 21:00 UTC (9am to 5pm US Eastern time),
 but interesting conversations can happen at any time.
 There are many different channels available for different topics, including:
 
-* ``#ops`` for installation help
 * ``#events`` for upcoming events related to Open edX
 * ``#content`` for discussions about course content and creating the best courses
 
 And lots more! You can also make your own channels to discuss new topics.
 
+Note that Slack is no longer the recommended communication channel to ask about
+technical issues. To do so, you should instead join the `official forum <#forum>`__.
+
 .. _Slack: https://slack.com/
 .. _Sign up for a free account: https://openedx-slack-invite.herokuapp.com/