Today Apple pushed out a firmware update for the 2012 AirPort Express. The current version is 7.8. This firmware adds support for AirPlay 2. AirPlay 2 was added with iOS 11.4.1 and will allow you to stream the same audio to multiple rooms, or stream multiple items to different speakers. The latest firmware allows you to use the AirPort Express as an AirPlay 2 destination.
It is important to note that this only applies to the 2012 AirPort Express, which supports 802.11n networking. This does not apply to the original AirPort Express. If the back of your AirPort Express looks like the one below, it will be able to support AirPlay 2.
In order to update, you will need to use the AirPort Utility to perform the update on your AirPort Express.
Even though Apple discontinued the AirPort line as of April, they are still supporting it for a few more years. It may not get many updates, but it is nice to see it getting some additional features.