I use Matrix, and I’ve moved some conversation with people I met in public rooms there to Signal because it kept failing to transfer keys rendering it unable to decrypt messages. I haven’t seen that in a while so maybe it’s fixed, but I haven’t been using it for one-to-one conversations lately.

Unfortunately, I’ve found most people have a lot of resistance to adding another messaging app. I don’t really understand why that is, but it’s true. Asking someone to install a messaging app when I’m their only contact who uses it and they have another way to contact me has a success rate near zero.