IRC for main chat, Mumble for voice chat when gaming. Been solid for decades. I have at least 3 functional Mumble servers saved (including my own) in my client, most of them are associated with an IRC community. I occasionally hear "Anyone down for some Quake? Hop on Mumble." or something to that effect. Mumble is pretty easy to host, so if you're using it with a small to medium group of friends, I'd say just throw up a server on your LAN somewhere. It's got decent mobile clients on F-Droid as well if you need one.

Not all gamers are techies though.

Some of my gaming buddies on Discord needed help getting that properly working. Asking them to set up and use both IRC and Mumble would be a step too far.

This is a common trap HN falls into. Stuff that’s easy and practical for people of our capabilities can be a nightmarish hellscape for other people.