A major characteristics that you need to decide upon is how searchable/disposable are you expecting the conversations to be. Coarsely you have forums, mailing l

A major characteristics that you need to decide upon is how searchable/disposable are you expecting the conversations to be. Coarsely you have forums, mailing lists, and chat options. My own open source projects are split between the different mediums. Chat via something like IRC on freenode (+ matrix if you want extra features) is easy to setup and great for casual discussion or very bursty conversation (time-zone permitting). Mailing lists make for decent multi-day and searchable conversation, but they can pose signal-vs-noise issues (freelist would be a good option). There are various options for forums (e.g. discourse) and they work well for longer lived, but marginally more disposable conversations compared to mailing lists. As long as you can pick something that the community is interested in using any option should be reasonably viable.