https://wccftech.com/tvos-14-3-is-now-available-with-fitness-for-apple-tv/

You can go right ahead and download tvOS 14.3 on your Apple TV HD and 4K. It includes support for Fitness+ service from Apple.

Apple made a huge song and dance about its new Fitness+ service a while back. Today, that service is available to everyone with the release of iOS 14.3, iPadOS 14.3, watchOS 7.2 and tvOS 14.3.