Telegram has off-by-default E2E encryption with a less vetted algorithm that only works for 1:1 chats, and less focus on minimizing server knowledge. That's clearly not
Telegram is not opensource, Signal is...and yes you can setup your own server with Signal. Why trust a Closed-source-Software? Do you even know that it is encrypted?
The encryption takes place in the client though, which you can verify by looking at the client source code. I find your comparison with Facebook a bit lacking, a better one would have been by looking at the Firefox code to verify if https traffic is encrypted.
> same level of e2e security