afaik that's their next step- introduction of usernames. Or you can use Element/Matrix, that is based on signal encryption protocol but does not need phone nr
In the time that usernames not phone numbers have been their "next step" they have introduced; gifs, encrypted audio and video calls, a built in scam crypto payment scheme, snapchat stories clone and a cryptographic upgrade to defeat quantum computing.
Changing from phone number to username is apparently hard.
It seems that the Matrix protocol offers optional end-to-end encryption on a room-by-room basis via Double Ratchet Algorithm that was introduced by the Signal Protocol [0]. This is the academic paper that Wikipedia cites for that claim [1].
[0] https://en.m.wikipedia.org/wiki/Signal_Protocol#Influence [1] https://link.springer.com/chapter/10.1007/978-3-319-45982-0_...
The core idea of the signal protocol is the ratcheting algorithm, which provides the actual qualitative security benefits, this the only real important thing.
Also he was explicitly stating it is based on it, I feel like you are arguing just, because you were so sure yet so wrong in your previous comment
I was only "pretty sure" in my original comment, not "so sure!" :)