My goal is to leave Facebook Messenger completely, but I'm not going to do that until I can get something setup to replace it that my friends will use.

I have set up a Spectrum transport and now I use Messenger with XMPP client, gradually migrating some contacts from the transport to native XMPP :)

Interesting idea, but it doesn't seem to solve the problem of a missing Android XMPP app that does video and voice.

Same. I'm currently using FB Messenger, Hangouts, Signal, Telegram, IRC, Matrix, Keybase and it's really depressing how only FB Messenger from all of those is in my opinion competitive for just group and private messaging. Everything else just lacks some really useful feature, not to say some of those don't offer a few new features, but they're not usually useful enough.