There is more reason to be concerned about Telegram than most other similar services.

Partly because it’s insecure by default, which makes a large percentage of conversations vulnerable.

And also because the team behind it is very susceptible to pressure from the Russian government, which is especially bad when it comes to these things. Even if some of them are based out of Dubai now, it doesn’t mean that they aren’t still at risk of coercion, either directly or through for example threats against family members who remain in the country.

If you don’t trust Russia, which you shouldn’t, then don’t trust Telegram with anything sensitive.