And you're not Mozilla (which does want to communicate with laypeople) so...
They are already working on botching it, since they've moved the Rust channel to a closed source alternative with no expectations of privacy: https://blog.rust-lang.org/2019/04/26/Mozilla-IRC-Sunset-and...
-- asking for a friend :-)
If you mean real-time chat, in my personal opinion, Discord is the best choice. Zulip is good, if you can deal with it being a bit weird. The other options are fine, but not great. You may have different opinions than me personally.