Developers and public beta testers who installedthe iOS 11.4 betaare noticing that Apple’s AirPort Express wireless base station is showing up in the Home app as AirPlay 2 speakers.
Of course, you cannot actually add your Express as a wireless AirPlay 2 speaker to your HomeKit setup because Apple has yet to release a matching AirPort firmware that would add AirPlay 2 compatibility to the Express, but it should show up as a compatible accessory.

Someonefoundthe file “airport_home.pdf” with the icon specifically for AirPort Express.
My house is full of AirPort Expresses so I’m very much looking forward to inexpensive multi-room audio when iOS 11.4 releases for public consumption. If you’re thinking the same, buy those Expresses now before they go out of stock (used ones are dirt cheap on eBay).
Currently, only the second-generation Airport Express model shows up in the Home app with iOS 11.4 beta 1 when you try to add a HomeKit accessory. People have been unable to add the first-generation Express routers—the Home app just hangs there without adding anything—but that’s something Apple might change in subsequent betas.

Just don’t hold your breath for AirPlay 2 support for the AirPort Time Capsule base station since it doesn’t have a built-in headphone jack nor any kind of audio output for that matter. No, there’s no audio component in the Airport Extreme base station either.
The Express is an excellent little Wi-Fi routerthat has always doubled as an AirPlay speaker and worked as a Wi-Fi extender. With its 3.5mm audio out port or optical audio via TOSLINK, you can easily hook it up to your existing home theater setup or plug it directly to speakers.

AirPlay 2 brings multi-room and multi-device control. With AirPlay 2, you can control audio playback and adjust volume across multiple AirPlay devices individually or at once right from the Control Center on iPhone or iPad, iTunes or the AirPlay menu on Apple TV.
Thanks to AirPlay 2, Apple TV also appears in the Home app as AirPlay 2 speakers.
iOS 11.4 and tvOS 11.4 betashave brought backother major features that got removed from earlier iOS betas, including Messages in iCloud, HomePod stereo pairing and more.