Initial testing suggests that AirPlay 2 isn’t currently enabled in iOS 11, tvOS 11 or both, according to AppleInsider. Hopefully, it will be added soon in operating system updates — along with other promised-but-missing features such as Apple Pay Cash (for iOS 11 and watchOS 4).
AirPlay 2 is Apple’s followup to the original AirPlay Wi-Fi-based music playback standard. While Sonos popularized Wi-Fi-based multi-room audio playback, Bluetooth became ubiquitous, and multi-platform Wi-Fi audio standards spread in popularity, Apple lacked a competing story until AirPlay 2.