Apple today released the third build of tvOS 10.2.1 to developers for testing on the Apple TV. This comes a week after beta 2 went live and before an initial rollout of the software update to the public. If your set-top-box is registered for preview builds of the OS, head over to Settings > System > Software Updates > Update Software and hit the download button.
So far, we’ve only been able to spot bug fixes and security enhancements in this build of tvOS 10.12.1. That said, if you spot something worth mentioning, you can tip us at firstname.lastname@example.org and @MBEDDEDMaximum on Twitter.