@vftdan
Is there any particular reason why you want to use the Linux PC for output only? Why not run mpd there so it handles everything — decoding, storage and output and control it remotely with mpd client like M.A.L.P. running on the phone?
@vftdan No, nothing comes to mind. Maybe you can make the computer act as DLNA media playback device and your phone as a server so you can use the computer as sound sink. Would not be easy on the battery, but I'd probably try digging in that direction.
I ended up using Bluetooth, I have bluez-alsa running on my laptops in sink mode so I can use any of them as a Bluetooth speaker, but that's not what you want 😕