A look at Telegram's claims that it's a "secure messenger" despite lacking default end-to-end encrypted messages and any E2E encrypted option for group chats (Matthew Green/A Few Thoughts ...)
https://blog.cryptographyengineering.com/2024/08/25/telegram-is-not-really-an-encrypted-messaging-app/
http://www.techmeme.com/240825/p7#a240825p7