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.
Probably this might be related to why tencent removed cloud backups from WeChat. It used to be like telegram, when you login it loaded all the previous messages, now when you login using the sms confirmation code you need to ask (with a different chat app!) three friends to send you a session specific passcode and then all the previous chat history is wiped clean.
(It was a problem to login back to me as I didn't have three friends)