Comment by NoboruWataya

I like IRC, but that seems to be an unpopular opinion these days (but maybe appropriate for a bunch of hardware hackers, since you could probably host it on an ESP32 if you were so inclined lol). There is also Matrix, which is somewhat more modern, or Zulip as another commenter has mentioned.

Ultimately it's your decision, and I guess Discord is probably easier to manage. Just consider that with Discord the discussions and knowledge that build up on the server don't really belong to you.