flux

I have mine hosted on elest.io. As easy as it gets. Just choose your software enter some initial domain setup and deploy. Can’t beat it for 18 bucks a month.

Revolt.chat is quite similar to discord and open source. They do run a centralized server to make it easy for everyone to get onboard, but it can be self hosted as well.

That being said, I still don’t use it because nobody else does, and that’s the problem with all chat and social media apps.