Remember that rumor about Apple locking out hacked Apple TVs? Well, their official word is that no, they don’t do that.
https://gizmodo.com/pirate-fighting-rumor-apple-locking-hacked-apple-tvs-247983
Apple’s just said they did not put a backdoor into the Apple TV and whatever you do with your box is your own business. Just don’t come around with a broken Apple TV box running Ubuntu Linux and expect them to fix it for you.
The official word from Apple: “We are not doing anything proactively at thist time, but if users hack their systems, they’re voiding the warranty.”