@digitalgyoza@mastodon.art No app is good if it requires your personal telephone number for registration. However, if we need to choose, there was recently a big research of three mobile messengers, including Telegram, https://encrypto.de/papers/HWSDS21.pdf
Considering from the found data, I would say that Telegram is more reliable than Whatsapp and Signal. Also, its founder is obviously opposed to governmental abuse of power and monopoly companies (for example, Apple).

Additionally, there are an amount of choices in useful bots (which you can also create for whatever you need; I can eagerly advise the bot that simplifies downloading of books/articles from sci-hub and libgen, etc.) and various channels (that may serve as a comfortable RSS feed from Reddit or whatever). If you chat with someone and that someone forwards your messages outside, you can hide your account to not be traceable. And other perks, such as proxy connection, synchronization with the server like Matrix, custom stickers, and further things I am not aware of or forgot to mention.

I hope you found my reply helpful in some way <3