As a fellow 2012 Denon owner (AVR 3313) you can probably remove the RPi and just use HTTP. Just use devtools on your browser to do an action in the web UI and see what request it sends, then replicate it in shortcuts.
And there's a internet radio capability built in - you have to pay $20 or so a year for it but it should be easy enough to set up a competing service since it uses unencrypted HTTP - probably just a matter of reimplementing the protocol and then DNS redirect.
And there's a internet radio capability built in - you have to pay $20 or so a year for it but it should be easy enough to set up a competing service since it uses unencrypted HTTP - probably just a matter of reimplementing the protocol and then DNS redirect.