Yeah I remember it was not that easy to set up, but it’s gotten a lot easier recently. I switched from the native to the docker install last year and was surprised to have it all back up and running in an afternoon…

I’ve been using jitsi meet for video calls for years now, that should work just fine.

Mumble has a very small footprint and exceptional voice quality. It’s intended to use while gaming as well.

Matrix seems a bit overkill. I think they would be better off with something like gotify.

Take a look at dontkillmyapp.com to see if your phone provider hinders your messages.

There is unified push as Google alternative as well, which works with the schildichat matrix client.

I’ve used jitsi meet (own instance) for this before. OBS might work as well.