My bad! Tried it with 19.1 on macOS and it indeed doesn’t work. I’ll hop over to the Kodi forums!
Edit:
If anyone is looking for a workaround, opkg install shairport-sync-mini does the trick if you’re using alsa. If you’re using pulseaudio (i.e. a bluetooth speaker) then it gets a bit trickier, but if anyone’s interested I’ll post instructions for getting it to work.