I liked Threema but it had the same issue of getting other people to use it. For me it was usually very specific individuals I wanted to share a channel with so it wasn't too difficult. But for more general contacts and friends there was no chance. And maybe that is ok in the end.
I've set Signal as my SMS app. When I message somebody, sometimes they happen to have Signal installed, and so it's a Signal message. Otherwise, it is a plain SMS.
