Telegram isn't serious about privacy. They made my number searchable and notified people who have me in their Google contact list even though I didn't grant Telegram access to my contact list (before the time when Android would enforce this with permissions) and didn't allow them to use my number for anything.

Then it turned out that they have a setting where one can opt out, but what good is that if you already were opted in automatically.

In "Last Seen & Online" I had a deleted account in the exceptions of those who can always see my status, even though I never added one.

Telegram may be better than WhatsApp, but it is far from fantastic.