Not fan of apps that required "phone number" including Apple/Google's lousy Messengers. Been using Riot.IM... now called Element; a [matrix] client. It's the only Messenger I use on daily basis. If UNA develop Element or [matrix], I'd switch in a heartbeat!
That is why i don't use OneSignal and not even una mobile app. If u want to share an image using una mobile app, it will ask permission to access all my mobile media, just like FaceCrook, Twatter and all those thieves.
