It was a many months transition, and it's finally done
Fun thing, you can actually make a backup of all* your messages, groups, contacts, etc. So before leaving you can have all of your data in case you need that one contact or something
The final red flag was as that allegedly Russian authorities were messing with people's deleted messages. Not for the first time there are news that they could read, modify, delete, see location, and etc. Screw it, this is unsafe, I'm out.
Also, these days telegram is really at the state of a pile of garbage, bloated, buggy, and shady messenger.
Easy! Just replace their usual SMS app with Signal, and then every contact they have that does use Signal is private and secure!
Oh. Wait. That's exactly the functionality that Signal removed in their effort to ensure that Signal is never widely adopted.....
I didn't agree with their decision at all at the time, but now that I realize they made it a little while after it gained widespread adoption and people stopped using it because "Signal isn't actually secure!" ... seems like people were expecting a secure messenger to be, well, secure. So they would chat about anything and everything thinking "I am using a secure messenger, these messages can't be read..." and tech ignorance is a dangerous thing if you're trying to be secure. I would've preferred a colored window and un-closable message for SMS chats, but oh well. I like that they've introduced usernames so you don't have to give out your real number.
And that irony now is that messenger on Android is RCS compliant and currently has this exact functionality, except it's less trustworthy.
Once again I'm using one messenger and everyone else who's using an RCS messenger gets encrypted, but SMS (clearly marked as such) is a viable fallback.