As Eldin said me yesterday, this part of the CH docs is no longer true:

Note that neither posts in Telegram Channels, nor group interactions with multiple users are managed by instances of this class.

I didn't check if that's true, so I don't exactly know whether ConversationHandlers can really work in group chats or channels. But if yes, docstrings should be updated on this case and any additional notes on using CH in such cases.