I found SimpleX recently (https://simplex.chat/), which got my attention because it uses a unique account schema that doesn't have any individual account identifiers. It's got some interesting features. Not sure about user-friendliness since I don't use other messaging apps to know what to expect.

It's mostly just interesting to me that they did away with the username entirely and they instead have users connect exclusively through shared secrets like they're Diffie and Hellman.

I don't have a good answer. Personally, I'm using Jami for secure communications but I won't pretend it replaces signal in terms of user-friendliness especially back when signal allowed SMS and secure communications in the same app!

Threema comes to mind.