I find the quality very good. And there’s no problems with setup a “server” :)

1. Go to the preferred Jitsi Meet server.
2. Enter the meeting name (as it really called) or just press enter to get a random name.
3. Enter your details and options (mainly mic on/off and webcam on/off).
4. Enter the meeting. If you’re the first one in it, you’re the moderator.

Once inside and as a moderator, you can create so called breakout rooms. These works just like subchannels in Discord. If you’re many people in 1 call, you can create these to create a more calmer experience. I have personally not tried these out since I have only talked to 1-2 people.

Mumble is a excellent VoIP software, but like you said, screen sharing is not possible since Mumble is just what VoIP means: voice over IP.

I have the same issue, but got 2 Discord users to try Jitsi Meet with me (a friend of mine on my Snikket server invited her friend). After a while, her friend asked me why it looked so much alike Discord and my friend agreed. I gave them a big smile and said, “because this is awesome”.

Jitsi Meet + Snikket has been my saves since I deleted my Discord account during the pandemic.