The first beta of tvOS 12 available to public beta testers corresponds with the second tvOS 12 update made available to developers. Developers have had access to tvOS 12 since June 4, when Apple introduced new versions of tvOS, iOS, macOS, and watchOS at WWDC.
The tvOS 12 public beta can be obtained by going to the Settings app on the Apple TV and navigating to the Software Updates section under "System." "Get Public Beta Updates" will need to be toggled on, and once it is, the Apple TV will download the beta software.
tvOS 12 introduces long-awaited support for Dolby Atmos, and when tvOS 12 launches this fall, iTunes will be home to the largest collection of Dolby Atmos-supported movies. As with the launch of 4K HDR, previously purchased content will be upgraded to include Dolby Atmos on all supported titles at no cost.
tvOS 12 brings a new zero sign-on feature that's designed to let cable subscribers watch live channels and on-demand programs that they're entitled to through their cable subscription simply by being logged into their home internet networks. This is something that will be limited to Charter Spectrum users to begin with.
Other tvOS 12 features include autofill passwords from the iPhone to sign into Apple TV apps more quickly, and support for Home Control systems like Crestron and Savant, which will be able to be used to control the Apple TV. Apple also plans to make the Apple TV Remote a default option in Control Center on iOS devices, and there are new aerial screensavers created with help from the International Space Station.
tvOS 12 will see a public launch this fall, and until that time, will be limited to developers and public beta testers as Apple works out bugs and other kinks.