Is there ANY way to send audio from linux to AirPlay speakers?
(I am NOT asking about making Linux an airplay TARGET, which is what Shairport-sync does.)
Pulseaudio reportedly used to claim to support it, but there are many reports of people trying and none of anyone succeeding.
If you can stream your audio via Google Cast, there are a few Cast -> Airplay bridges. I have one of these running on an RPi (I believe [1]), and it's been pretty much fire and forget.
RAOP Discover is currently at the point «It just works until it doesn't» (like most things zeroconf). Behaves fairly reliably in my experience if you don't mind some latency.