Given the location of Telegram's servers (Dubai), and the nature of the government (neutral dictatorship) and the lack of encryption, my default assumption would be that not only are they selling access to your data to major governments, they've probably even streamlined the bidding process.
"Ah, but if you need encryption then you'll..." - well, two things now. Suddenly you're the person who has encryption switched on. And also more likely, someone they talk to will forget to switch it on and just blab everything into cleartext anyway.
The entire importance of Signal's model is that it is always encrypted. It's why LetsEncrypt is also important: to have effective security you need to be able to hide in the crowd. If encryption usage is rare, then who's using it itself (or suddenly starts using it) becomes an extremely valuable datapoint.
(so I'd add: Telegram absolutely sell timeline details of which user accounts change their frequency of encrypted chat usage).