F-Droid

I do but not an open source one. Basically just use Google's with rcs disabled because for me the rcs messages only resulted in me getting a could not be delivered message 3 or so days later (I'm in the UK I hear it actually works elsewhere but yeah I've never sent one that actually delivered). I think it's a common thing here as I've had to disable rcs on several relatives phones because their messages didn't deliver at all and that's most of the main phone networks

To be honest though I do use Signal more than Sms but it would be silly not to have it all on a phone.