I also thought you could create an account without your phone number nowadays, but since I already have a phone-connected account, I haven't tested. Only thing I found in their blog was this: https://signal.org/blog/phone-number-privacy-usernames/

Until now, someone needed to know your phone number to reach you on Signal. Now, you can connect on Signal without needing to hand out your phone number. (You will still need a phone number to register for Signal.) This is where usernames come in.

There are some newer post about other changes, but I haven't checked them in detail.

Pretty recently I think