I've installed Moode Audio on a Raspberry Pi and hooked it up to my living room sound bar alongside the #Chromecast Audio. It can't do casting but it can do AirPlay.
But that's a somewhat inferior solution, since for the most part AirPlay doesn't hand off streams for the target device to handle on its own, you're actually streaming from the sender device, using its resources (e.g. battery, CPU, bandwidth), and you can't close the app. So I really hope Google fixes this thing.
@pieist @LateNightLinux Yes, it doesn't look like there is much in the way of an OS alternative. I very much want to handoff the playing to another device - means I can do something else on the phone or laptop without depleting the battery too.