I know Teamspeak 6 is in beta, so I get it. But boy when I tried it, it was just awful. It took me literal minutes just to figure out how to disconnect from the voice server. They desperately need to hire someone for UX who has actual experience in, you know, design.
And getting Matrix (Synapse) to run is about as teeth-pulling as getting an Oracle database system to run back in 2001.
I don't like what Discord is doing. And I'll likely find some alternative if I can convince others to also join me, but there simply is no viable alternative that gives the exact level of experience that Discord does (from a feature point of view and a UI/UX point of view).
And yes, I've tried Fluxer. It's a good start, but still needs a lot of work, which the maintainer says is ongoing (work such as making self-hosting viable, etc). While I like the UI/UX of Fluxer, I am concerned that its UI is effectively a direct copy of Discord from a few years ago and I don't know if Discord would be legally able to do something about this. Perhaps it's all fine, and if so, I wish Fluxer immense success at being that viable Discord alternative, and I will keep an eye on this project.