Peter
Oh, I see. Yeah, that channel I linked above is bridged meaning you can access it through different technologies so people can use their preferred chat clients. Element is a client for the Matrix protocol. XMPP is another protocol.
Mumble is the voice chat server. You should be able to join that with the Mumble client.
And yes, there were four of use on OpenSpades for the testing. It all worked well. We also tried OpenHV and Xonotic. I plan to organize a real event somewhere in the beginning of March.