Using apps based on Google Play Services may be impossible on those phones out of the box (not sure), but websites have no such dependency and most people don’t give a crap about push notifications from PWAs anyway so whether FCM works with the device matters little. Also doesn’t the web push API support different push services at registration time so those devices’ browsers can register their own vendor push server? (It’s been a while since I implemented web push myself, memory is fuzzy.)
This is blocking access to websites wholesale, so it’s on a whole different level.
