FYI my ~9y/o marantz is also hardwired, but I cannot get airplay to work unless I explicitly go to Net/USB and even then it's the same 2-3 attempt (switching inputs) to get the device to appear on the airplay list. After that it's flawless, but the UX pretty much means I'm the only one airplaying to that device. I have since upgraded 3 years ago to a newer slimline model and that has no problem being found regardless of the input used and regardless of wifi/ethernet.
My friend with a ~5 year old denon also has no problem. So possible this is a discontinued firmware issue. YMMV
My friend with a ~5 year old denon also has no problem. So possible this is a discontinued firmware issue. YMMV