A recent report has proven that Telegram sticks to its promise of keeping its user data private, while apps like WhatsApp give real-time user data to third parties, and despite their numerous claims about "E2E encryption", can also disclose message contents.
I am not surprised. Most other apps couldn't guarantee privacy to their users even if they wanted to. Because their engineers reside in the US, they have to secretly implement backdoors in their apps when the US government orders them to. If an engineer speaks publicly about it, then can go to jail for breaching a gag order.
In most cases the agencies don't even need a court order to extract private information from messaging apps such as WhatsApp, and in other cases, court documents are shrouded in secrecy. Some supposedly secure apps have been funded by government agencies from their inception (e.g Anom, Signal).
For many years the National Security Agency (NSA) has been making sure that international encryption standards are in line with what the NSA can decipher, and all other approaches to encryption are labeled as "non-standard" or "home-brew". Through their proxies in the encryption industry (like this one), the NSA imposed flawed standards onto the encryption used by the rest of the world, cautioning everyone else from "rolling out their own encryption".
No wonder US-based apps such as WhatsApp are plagued with backdoors – intentionally planted security loopholes that governments (and anybody else) can use to hack smartphones and extract private data from people.
I hear our US-based competitors are frustrated that they can't match Telegram's growth, despite heavily investing in marketing (something Telegram has never had to invest in). But in order to match our growth, they have to first make sure their actions match their marketing claims. Until then, data breaches and security issues in their apps will, unfortunately, remain unavoidable.