There are so many convoluted and contradictory statements saying YouTube isn’t on the newest version of AppleTV or It is but very janky. So does the regular YouTube app work on the newest version of AppleTV and AppleTVOS with the YTPremium benefits??
Enable stats for nerds on YouTube while watching a 4K video and confirm for yourself. YouTube all has always played 4K videos on the Apple TV 4K models
Not always. 4K support in YouTube was added in 2022 with tvOS 14, which added software-decoding for the VP9 codec YouTube uses.