2 that I know of, but that’s the majority of my social circle (not working, no family). The other people I don’t think would want to because it’s different and difficult and those are “leave everything at default” sort of people when it comes to tech, so lost cause anyway.
Both the people who do use it are there because of me, though!
My partner and I were struggling when I was android and they were iOS, there was delays that threw everything out of order, so we tried a few messaging apps that worked cross platform and I found signal and we started using it together, and my friend started using it when dating a new person because e2ee for naughty photos and stuff, at my suggestion. They were using Snapchat and I was like ummmm.. no. Don’t do that. But we use it to talk all the time now.