From the Telegram blog: Chat Export Tool, Better Notifications and More

I think you need to install Telegram Desktop to do this.

To delete your account you will need Telegram on your phone to receive the confirmation code (not SMS)

Delete account: https://my.telegram.org/auth

The Reddit topic in the screenshot is just as quotable and directly points at the root of the problem:

“I need privacy, not because my actions are questionable, but because your judgement and intentions are.”

Are “name checks out” posts allowed here? Beetlejuicing?