Forums. Phpbb, Mybb, hell even discourse is better than discord. If you’re specifically dealing with a coding project, most git repositories offer an issues page and wiki you can use.
And if you want something realtime, IRC & XMPP are low-resource chat options—with the latter being federated & can offer encryption for private rooms.
Sure, but those options solve literally none of the issues discussed above
There’s still been a time & place for realtime communications where the history preservation doesn’t quite matter… it can be some general recon of a problem to know what to even ask so as to not clog up the signal-noise for SEO or even if it’s mostly off-topic banter to relate to community members.