I have never known anyone using E2EE on Telegram. A friend of mine who uses Telegram regulary was quite surprised when I told her that nothing is encrypted if she doesn't use the 'secret chat' option which she didn't really seem to know about.
I'm not deep in to the technology and politics of telegram but I don't use it exactly because I know that letting the default be insecure is a common used dark pattern elsewhere. And that doesn't inspire confidence.
