"Telegram clearly fails to meet this stronger definition for a simple reason: it does not end-to-end encrypt conversations by default. If you want to use end-to-end encryption in Telegram, you must manually activate an optional end-to-end encryption feature called “Secret Chats” for every single private conversation you want to have. The feature is explicitly not turned on for the vast majority of conversations, and is only available for one-on-one conversations, and never for group chats with more than two people in them."

indeed worth the time