Apple on Thursday released the second beta for tvOS 9.2.1 to developers. To update, you’ll have to connect your Apple TV 4 to a computer via a USB-C cable, and install the software through iTunes or Apple Configurator.
Todays release comes a month after Apple pushed out tvOS 9.2 to the public. That was a significant update, bringing about new user-facing features such as support for Home screen app folders and Bluetooth keyboards.