So in preparation for tonight did some tinkering on HDR and my existing PS4 and why I never thought it was working.
Turns out on the Yamaha receiver i had to go in to advanced setup (straight button + power) and change from 4k Mode 2 to 4k Mode 1. Then in the TV (Samsung 65KS8000) had to enable HDR color output on HDMI-4. Went back in the PS4 and now says HDR enabled.
Why this is not automatic is beyond me, but it appears to be happy now. The TV does a piss poor job of notifying you though. I don't think any of the built in apps pop up an HDR banner and you can only check by verifying your settings (light, contrast, etc) have been automatically kicked up.
*Edit: I take that back, the Amazon Video app does notify you. But PS4 and Netflix or YouTube do not.
This turned in to a TV / Receiver blog post and not RDR, heh.