Yes, it;s Roon. Put the Roon core on your HTPC. You can even stick with windows if you want. Roon will see your AVR as an audio device that you can control from anywhere in your house with a laptop, tablet or phone. Use Pi4s as extra endpoints for other zones around the house. Or get your hands on some Chromecast Audios (they're still available from ebay or the UK). A CCA is a stupidly good endpoint for Roon. In fact one drives my DSP for my 4 channel K510 rig. Sounds amazing.
Feel free to PM me with questions, I've been a Roon user for a couple of years now and been doing linux audio on Pis for maybe 4. I submitted a couple of bug fixes even for Volumio's airplay support.