Comment by einpoklum

My stance on interaction mechanisms "to support developer community":

For any project size:

1. Issue tracker.

2. Mailing list (or similar mechanism) for announcements (not discussions with the users).

For a larger project:

3. Forums

4. IRC/Matrix channel for chatting ... if core developers are chatty enough to sustain this.

For an even larger project:

5. A publicly-editable wiki and/or a Q&A platform

6. Multiple chat channels, mirroring them on different chat platforms

I'm not saying nothing else works, only that this ladder seems to work well on the projects I have encountered.