I’ve been using Telegram enough to understand that such allegations are useless. The first link is literally not about Telegram but about its 3rd party fork that original developers can’t do anything about. The second link is about piracy, and any app owner would handle any data they could in similar situations.
Telegram is not just a messaging app but a public platform with channels and public chats. Any app with these properties will eventually have the same issues. If you don’t want to risk, you just use it as a personal messaging app and that’s it - in this way it’s not much different from other “secure” messaging apps.
The way for apps like Signal to remain “truly secure” in “careful” users’ eyes is avoiding the introduction of the public communication part, which could lead to all the same problems some people don’t like Telegram for.
That said, Telegram actually has a history of being a “bad actor” if you want to call it so. Namely:
At first it was possible to steal someone’s account by faking a SIM card (any government can do this). Later Telegram introduced cloud password that helped to prevent such cases.
At various points Telegram wrongfully banned and marked as “fake” various channels and bots used by opposition in Russia.
But I can’t agree that either of that makes Telegram an insecure messaging platform. It’s either about bad management decisions in specific situations (e.g. Durov being worried about Telegram getting banned) or technical aspects of how user reports are handled (basically any channel can get marked “fake” if enough user reports are received).