Telegram is giving away FREE Premium subscriptions! All they need from you is to use your cell phone as a relay to text out their OTP codes! And the recipient of the OTP sees your phone number! What could POSSIBLY go wrong with this deal?
PLEASE don’t use Telegram! I personally recommend Matrix as it’s totally FOSS, you can self host, there are tons of front end clients to choose from. Or even use Signal. I have my own issues with Signal, the fact they don’t allow third party clients, you can’t self-host, they have a proprietary shim in their stack that only they know what it does, they were pushing crypto, etc, but at least Signal is better than this garbage.
And it can’t die fast enough, as it’s essentially the same as broadcasting your sensitive information over unencrypted radio.
Apart from security, phone number based user identification is such a half-assed approach and I still don’t get why Signal wants to die on that hill. It’s inconvenient, yet trivial, for anyone to register a second, third or tenth phone number. With a bit more knowledge and inconvenience, even anonymously. It adds so little.