Zulip offers an open-source solution for web-based organized discussions.

The open-source version is the full version, with access to all the features, no open core. That's a good incentive to use this instead of Mattermost.

Plan would be:

• deploy open-source versions of Zulip as Docker containers
• add social login from GitHub, see if we can use DevCentral too pending an unified SSO solution
• bridge IRC channels and Zulip

See also: T2128 for Mobile push notification service