I am going to start again as I've done a lot of troubleshooting since my first post.
I bought the W2700 and a Chromecast Ultra this week. My first leap into 4K and HDR. I have been going INSANE over the past few days.
What I have discovered is, Chromecast Ultra into projector works fine with HDR. Chromecast Ultra via my receiver (VSX-830) doesn't work. Yes, this receiver is meant to pass through HDR and 4K. If I have the 4K setting to 4:2:0, it passes through 4K, but doesn't detect anything as HDR. So any HDR content looks awful. If I set to 4:4:4, I can hear the audio, but no image.
After hours and hours or troubleshooting, I happened to stumble across a cheap newer receiver at my local retailer for $180, so I bought it. The Yamaha HTR-2071. I figured if I can get the Pioneer returned under warranty, at least I won't be waiting for weeks for a receiver.
So, THE SAME PROBLEM HAPPENS ON THE YAMAHA...again, it's advertised to support 4K and HDR feed through. What am I doing wrong?!? I eventually threw in the towel and decided I'll have to live with Chromecast direct into projector, then audio via ARC...but I have discovered that only delivers stereo audio, not 5.1...
I have also tried a different HDMI between the receiver and projector. No difference. Both are 'high speed' cables. All that is left is to try another 4K device, incase this problem is isolated to the Chromecast Ultra. I feel that is unlikely and it will just be more money down the drain for me to buy another 4K device. It's been like four days and I havn't actually got to watch anything on my new projector