That doesn't feel simple. I installed Signal.
What doesn't feel simple from the user perspective?
Get https://play.google.com/store/apps/details?id=im.blabber.mes... , start it, follow the screen.
Or https://gajim.org/download/ for desktop, register on first run.
Or https://siskin.im/ for iOS, register on first run.
If that's not simple enough, we need to nuke the whole smartphone scene.
+ the steps above were _my_ steps, the steps of an XMPP server provider, not the steps of a user.
Because asking them to install another app on the phone is?
Seriously, what's the difference?
If you want to avoid Google Play-Services then Element and ActivityPub are much easier to use.