I have been watching KODI, PopcornTime and Livewire working great all installed on my AppleTV 4 for the past 2 months. Here's the instructions.
Here are the IPA's you can download and drag to Cydia Impactor 1 at a time for installation onto Apple TV.
This will only last 7 days then you will have to delete each and reinstall it again using the above method.
If you are looking for something longer term you would have to sign up as a developer with apple which would cost $99 a year. Each IPA installed would then last 1 year.