Yes, I believe it has something to do with the new changes implemented because of the usernames.

Well, let them know about it, you have few options for that: GitHub, Official Forum or Signal Support website (how to get debug logs? read here).

There is also unofficial instance on Lemmy, cross post it over there.

I have the same problem on Signal (PNP), custom rom.

c’mon Signal, gimme that apk & I give you some logs in return, don’t make it hard on me