From my quick testing I did the other day, the conclusion I came to was:
- Fluxer looks like the easiest drop-in replacement for my group. I agree I am also a little hesitant about its longevity & funding.
- Matrix UX leaves some to be desired, but it's functional and I like the E2EE.
- We don't have anyone good enough at selfhosting in my group to even attempt Spacebar.
- Stoat just doesn't seem viable. Lack of screenshare is a big issue for my group.
Surprisingly, the new TeamSpeak 6 looks pretty okay to me, but the UX is pretty different so might have a little bit of a learning curve for some people in my group. It costs money for a server but honestly my group is fine with that. We used to pay for a Mumble server back in the day but it doesn't have robust text channels so we don't want to move back to that.
It seemed like it would work for me. The user experience is pretty different than Discord, but I caught onto it pretty quick. There are public servers you can join to see what it could be like. When you launch the desktop client, there is a "popular servers" section on the home page that lets you pick from a couple different community servers. I joined the "Official TeamSpeak Community Server" and then just jumped into the Counter-Strike channel and played around, tested streaming, chat, etc.
To be clear this is the TS6 client, not TS3.
As far as I can tell you can't actually test creating your own server before you pay for a community, although the cost is cheap ($5 USD a month) and it looks like there is a trial.
From a longevity perspective, TeamSpeak might be a good choice for my group, since it's been around in some shape or form for like 30 years at this point. My group has moved like 3 or 4 times. Not sure if we'll find a forever home but the longer we can stay somewhere, the better.