Comment by toyg

If i remember correctly, Telegram pre-dates Signal by several months. It was well-established by the time Signal became usable. This said, the relationship between Telegram and the cryptography community has always been rocky, probably because they touted their E2E support as a differentiator from the start (Whatsapp, Messenger, and whatever-Google-had were not e2e at the time) but quite a few people pointed out their implementation was weird and broken (it has since changed).