Heliography in darkness
Telegram doesn't hold up to the promise of being private, nor secure. Theend-to-end encryptionis opt-in, only applies to one-on-one conversations and uses a controversial homebrewn' encryption algorithm. The rest of this article outlines some of the fundamentally broken aspects of Telegram.
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Telegram is not a secure messenger, nor is it a platform you should want to be on. Chats are not encrypted by default, and are stored in plain text on Telegram's server. Only chats between two (not more!) people who also happen to both be online at that time can be encrypted". In addition, the quotation marks highlight another massive issue with Telegram: its encryption" is non-standard, home-grown, and countless security researchers have warned against relying on it.
Telegram's issues go even further than this, though. The application also copies your contacts to its servers and keeps them there, they've got a People nearby" feature that shares location data, and so much more. The linked article does a great job of listing the litany of problems Telegram has, backed up by sources and studies, and these alone should convince anyone to not use Telegram for anything serious.
And that's even before we talk about Telegram's utter disinterest in stopping the highly illegal activities that openly take place on its platform, from selling drugs, down to far more shocking and dangerous activities like sharing revenge pron, CSAM, and more. Telegram has a long history of not giving a single iota about shuttering groups that share and promote such material, leaving victims of such heinous crimes out in the cold.
Don't use Telegram. A much better alternative is Signal, and hell, even WhatsApp, of all things, is a better choice.