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.
I never got with these russian authority claims. Telegram is not based in russia, sure its founders are born in russia but they have taken citizenship of France for a long time now, its based in saudi arabia. I never saw a single proof of them giving data to russian authorities, they were banned in russia for that iirc but eventually got unbanned due to mass adoption. At this point these russian claims just seem racism to me.