"jitsi.meet sounds like a good idea until you realize you need a really fast
connection (optic fibre is recommended)."
My experience testing it (and Palava.tv) is that it definitely doesn't work
without a fast PC, and fast internet. Now that I have some more powerful
hardware, and fibre to the door, I'm keen to give it another go.
But if you just want voice chat, I highly recommend Mumble. I've used it for
conference calls with a web dev team of 5 and it worked really nicely, even
on my poor old network (click on my username to see the specs) on a DSL
broadband internet over copper. It has clients for most platforms (certainly
all the currently popular ones). I haven't tried running a server though, I
just found a gratis one to use.
Has anyone tried GNU Ring? It's a P2P voice (and video?) chat app that
recently joined the GNU project.