Discord too.
I wish people would use open tech like matrix more. It's perfectly suitable for this also.
I don't mind Telegram so much but Discord wants a lot of personal information through its PC client. So I don't really use it even though some open source projects unfortunately do (like Home Assistant)
> A decentralized network based on cryptographic keypairs and that is not peer-to-peer, it is super simple and scalable and therefore has a chance of working. Read more about the protocol. You can also reach us at our Telegram group (while we don't have a decent group chat application fully working on Nostr).
Telegram really has captured quite a role as a functional forum / irc channel.