This might be common knowledge by now considering how easy it is to find this repository, but it’s new to me so I’ll share: apparently, the desktop app developer is actively working on rewriting their app using tdlib.

Telegram Desktop would be the first official app to use tdlib. Right now, the only telegram-related app that uses it is Telegram X, which is an experimental app. The bot API, though, has always ran on tdlib since day one.