One thing that worries me a little about fluxer is this:

Finally, we can offer commercial licences to companies that want to run Fluxer internally without being bound by the AGPLv3 copyleft terms. This is enabled via a contributor-friendly CLA, but it doesn’t create a separate “enterprise edition”. It’s still the same Fluxer software everyone else uses.

• https://blog.fluxer.app/how-i-built-fluxer-a-discord-like-chat-app/

They have a CLA on contributions. So while today Fluxer is licensed as AGPLv3, tomorrow they can pull the rug and change the license, just like everyone else has been doing.