mumble and teamspeak. big win here is that throu self-hosting one can pick the optimal place i.e. an isp "in the middle" or otherwise local to the participants

mumble and teamspeak. big win here is that throu self-hosting one can pick the optimal place i.e. an isp "in the middle" or otherwise local to the participants. just stay away from places that host a lot of content (ovh, hetzner, big-cloud)