I recently set up a Mumble server on my home server and it seems great so far, was able to get my friends connected pretty easily. We'll see how the voice quality and latency compare to Discord.
Huh. I’d have said majority. It was always my impression that a) gamers make up the vast majority of discord users (with all their gamification and gaming features), and b) that gamers mainly care about voice chat (which is what people almost always talk about when it comes to discord and gaming).
Myself, though, I basically only use it to talk to the same guys I've been gaming with since we met in middle school 20-some years ago, and for that Mumble seems perfect.
That makes you an even smaller minority unfortunately. Most people are not going to set up a home server.
I tried this in the past but it didn't work. Now if your friends want to play you need to start the server for them. What if you're not at home? You basically end up making your pc a 24/7 server. Or you need to coordinate so that someone else runs the server in those cases, but that ends up creating more confusion. And let's not start talking about port forwarding issues...
All these issues are solvable, but they add so much friction when all you want to do is play with some friends.
It requires next to no CPU time, since the server is effectively just a packet relay.