Thanks. As mentioned I found Nextcloud difficult to set up (though that's not a showstopper, since it's a one time thing and users don't have to deal with it). But its web UI was imho poor. It was way too easy to click the wrong thing and have the UI suddenly change. I remember deciding my mom would probably find it unusable. The Android app had some issues as well, but I don't remember what they were. IIRC one of them was some obstacle to getting push notifications from the server without some kind of Google Play enrollment.

I'll try setting up Jitsi, though I remember thinking the setup looked daunting. Nextcloud and maybe Jitsi were both fairly hungry for server resources when the server side should really be very simple. Just some simple TCP proxying for multimedia plus a ZNC-like scrollback buffer for text.