Earlier today Apple released the first beta versions of iOS 11.3 and tvOS 11.3. There are not many new features in tvOS 11.3 yet, which cannot be said for iOS 11.3. Both updates contain support for AirPlay 2 with multi-room music playback.
If you have several Apple TV (4th and 5th generation only), then you can play the same music through them simultaneously.
For the first time Apple presented AirPlay 2 at the 2017 Worldwide Developers Conference together with iOS 11. However, the function will only be released with a public release iOS 11.3 and tvOS 11.3 this spring.
When you install the tvOS 11.3 update, you will be prompted to add the device to HomeKit by linking it to a room. After that, it will be displayed in the Home app. So far, with AirPlay 2 you can only play music on multiple devices at once and nothing else. However, there is still a couple of months before the final release of iOS 11.3, so Apple will have time to add more functionality.
Support for AirPlay 2 on HomePod will come with one of the system updates. Owners iPhone will be able to play one song through multiple smart speakers at once. In addition, AirPlay 2 will be available for third party speakers from other manufacturers.