After downloading the firmware update, AirPort Express users have reported being able to target the AirPort Express right alongside other AirPlay 2 devices when running iOS 11.4.1 or iOS 12. With the AirPlay 2 update, 2012 AirPort Express models offer support for multi-room audio and are able to work with other AirPlay 2 devices such as the HomePod, the Apple TV, and Sonos speakers.
This is great news for people using AirPort Expresses to power home audio setups. Good on Apple for brining support for AirPlay 2 to a device that has been discontinued.