None that aren’t at least in some way corporate. Maybe in another life, who knows. Or in a few years we’ll have something that’s actually useful and not corpo owned. With that out of the way, I’ve heard of but not tested these two:

• Guilded is basically discord but not yet enshittified
• Revolt.chat looks interesting, seems to be still in beta, is European, and iirc it’s developed by a non-profit