Oh, i see your edit now. I did a little testing, sadly this only applies to rooms with two people (including you) only, so it only functions like a normal 1:1 call (there's group videochat tho)

What’s the telephone icon then on the linked screenshot

If you mean my very top comment, there's no telephone icon :p I guess you mean that person symbol? Those are DMs :D

Or is it like only 1to1 calls

Yep

multi user rooms to join like discord/teamspeak u mean?

Also yeah sadly. If you're insistent on it, as i said mumble is a good choice; FOSS, not tied to one server. Here's a link https://www.mumble.info/