Many in the crypto and privacy community mistakenly trust Telegram because it's "end to end encrypted", but there are huge issues including not hiding the metadata, censorship, centralization, and phone numbers.
Send this video to your friend that asks why you won't join:
https://video.simplifiedprivacy.com/why-telegram-sucks/
Wow, not to pick on the narrator, but this comes off like the worst small town used car dealership TV advertisement I've ever seen.
Here's a real rundown I've put together over the years:
Pavel Durov's argument is that there should be a high functioning UI/UX experience for "non-secure" communication, and when you need it there's something much closer to Signal's very secure client-to-client encryption.
Arguably Telegram secret chats are even "close enough" to cloud chats an adversary might not notice you're doing the "super secret things" (making it harder to identify what to target).
They also provide verified builds even on iOS (though it's a bit of a hack, not "really" quite the same thing).
The only things that can really be said about Telegram's secret chat crypto are that:
It's not "the default"
It's their own crypto (i.e., they broke "rule #1" and "rolled their own")
Ultimately though, it's been just shy of 10 years since Telegram entered the scene, and nobody has actually broken Telegram crypto in any meaningful way -- AFAIK, to this day. Still, there are hypothetical holes in the crypto when scrutinized vs something like signal. So, is it as good as Signal or Threema? Eh, probably not, is it good enough for the average person that isn't target by a nation state? I'd say probably.
And for most people, it doesn't matter. It really doesn't. I'm not even going to argue about that. I personally couldn't care less about instant messaging with anonymity; anonymity and private are completely separate concerns.
I dont know what happened, but unfortunately that article is misinformation.
I was excited to sign up for telegram without a phone number, but the very first thing it asks you when you open the app is to enter your phone number. It won't let you proceed without it.
It's not misinformation, but it's also not free. You have to "get a fake number" of sorts from the Fragment blockchain.
I don't know much about those specifics because I live in the US, and fragment doesn't work here (due to conflicting views with the FEC). In theory, a VPN might let you do what you want even if you are in the US.