Meanwhile, Signal still requires a phone number to register and use. It's terrible: phone numbers are easy to lose, and not everyone has a phone number.
I like the ideas behind the Session[0] messenger: create an account with no authentication (no phone number, no email, no nothing), get a list-of-words-to-note-down, which allows you to access your account from any device. You get a UUID or something as your user id. Share that with a QR code or send a link over an existing channel to connect to someone.
To me this seems way ahead of Signal. I'm not affiliated with Session and haven't actually persuaded anyone to start using it just yet, so I don't really know how it is in practice. But the UX of creating an account made me weep tears of joy and hope <3