Following yesterday’s developer betas, Apple has seeded the second iOS 11.4 and tvOS 11.4 public betas. iOS 11.4 includes both AirPlay 2 and Messages on iCloud for testing, and tvOS 11.4 can be used for AirPlay 2 testing.
tvOS 11.4 Stories April 17
tvOS 11.4 Stories April 16
Apple has released the second tvOS 11.4 developer beta for testing on Apple TV 4 and Apple TV 4K. tvOS 11.4 turns Apple TV into an AirPlay 2 speaker which supports multi-room AirPlay from iOS.