I remember T-mobile enabled RCS for Samsung’s text app, but excluded unlocked devices. I was able to find some dial tone command work-arounds to force it to enable, but eventually some Samsung update took away the ability. But then a few months after that I installed Messages, so now I have it everywhere. Very handy when I’m inside a building and need to text. Doesn’t change the fact that I have like 3 regular contacts who actually use Android