Are my normal telegram chats encrypted on cloud and only decryptable by the user?

I have been reading about privacy with regards to telegram and signal. I have found out that the telegram secret chats are comparable to signal chats (end-to-end).

My question is about normal chats (with cloud backup, which are accessible on multiple devices), are they encrypted on the cloud?

or are they stored in plain text?

If they are encrypted, are they only decryptable by the user?

I couldn't find any official response or statement on telegram's website.

Thank you.

cloud encrypted privacy telegram