If your RAOP/Airplay doesn't work on Pipewire with apple devices, but does work with shairport-sync, open UDP ports 6001 and 6002.

These are used for timing and control, and apple devices won't play a single frame without first connecting to them, whereas shairport don't block on that as violently.

Yeah... one of those things that took a bit too long for me to debug — I've just thought that apple devices are intrinsically shit and won't connect cause they could — but nope.