The Home app is once more spotting the AirPort Express in iOS 12, raising the hopes for devotees of the now cancelled hardware.
was able to verify the appearance of the 2012 redesign of the AirPort Express in the Home app after three attempts. However, when tapped, the device is not added as a HomeKit peripheral -- but visibly fails unlike the first time around.
The last update to the AirPort express was in December 2017, for the KRACK exploits from earlier in the year. AirPlay 2 wasn't in testing at the time, with the AirPort patch happening well after the first round of testing of the technology, and before the abortive second round with the iOS 11.3 betas prior to its removal very near the end of the cycle. The update prior to the KRACK fix to the AirPort Express was delivered in December 2016.
The appearance of the device in the iOS 12 beta is the second time that it has appeared as a possible HomeKit accessory and AirPlay 2 target, and done nothing when selected. It was pulled about two weeks after the first iOS 11.4 beta.
Since that appearance, Apple has killed off the AirPort line in its entirety.
At present, again, the appearance of the old hardware appears to be nothing more than an aberration of the testing process -- but the fact that it appears at all rekindles the old mystery. It is obviously related somehow to the device's AirPlay functionality, as the the AirPort Express has been a playback target for some time, since when it was originally called AirTunes.
Once again, other AirPlay-compatible devices were tested after the re-appearance, with none appearing in the Home application.