the fact that E2EE is opt-in already makes this app ridiculous
in matter of privacy, yes. But it have cool features so.
They’re stored in plain text on Telegram servers No, non secret chats use mptroto but with different schema, thats not plain servers. And no data breach have been reported in telegram yet if it was “that” easy to breach them. From my last comment: “Also the research you shared is based on mtproto 1.0 which telegram abandoned almost a decade ago and there have been No such defects found in mtproto 2 yet.”