I was in a similar situation. Everyone says that you shouldn’t really push too much with these types of things. Once when I was fed up with nobody coming to signal I asked everyone, (even distant family and friends when I saw them), one by one to give me their phone and I installed signal on it, told them to activate it and told them that this is the way to talk to me. If you want to talk to me this is how they do it. It was a little bit weird, but now everybody, almost everybody, I want to talk to is on signal now and they use it to talk to me too.
Some of them I even got to use element/matrix on PC.