If your key goal is to play back Spotify using the native Spotify app, you might be better off just buying a cheap
Spotify Connect supporting device/dongle like a Google Chromecast or Amazon Firestick. You could then connect it to the HDMI IN port on the Oppo.
Probably vast overkill for your needs but you could also
install Logitech Media Server on your PC and then enable the UPnP/DLNA bridge,
Spotty and Material Skin plugins under System Settings->Plugins. LMS with then make your Oppo appear as a 'virtual' Spotify Connect endpoint. But this does requires some setup and also needs your PC to be switched on while you're streaming music.
The Oppo supports UPnP/DLNA so you could use the
mConnect (
free 'lite' version) or
BubbleUPnP DLNA controller apps. But neither supports Spotify, so you'd need to switch to a different streaming service.