tvOS 11.4 for Apple TV 4 and Apple TV 4K is now available after a few weeks of developer and public beta testing. The latest software update supports AirPlay 2 alongside iOS 11.4 which was also released today.
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After updating to tvOS 11.4, iPhone and iPad users running iOS 11.4 can see Apple TV 4 and Apple TV 4K in the Home app alongside other HomeKit devices. Apple TV will have you assign a room after updating, then you can see now playing content and toggle playback on Apple TV from the Home app on iOS.
Apple TV connected speakers become AirPlay 2 speakers as well. This means you can tell Siri to play music or podcasts on Apple TV in a specific room from Siri on an iPhone, iPad, or HomePod when running the latest software version. Siri on Apple Watch and Mac are left out for now.
Apple TV becoming an AirPlay 2 speaker also allows you to play to multiple AirPlay 2 speakers simultaneously. For example, you can play audio from iOS or iTunes on several HomePods, Apple TVs, and other AirPlay 2 speakers at the same time.
You can also target multiple speakers from Apple TV when running tvOS 11.4 now.