I have a Samsung KS8500 TV with a Roku ultra fully updated and just recently after a full year of no issues my Roku when watching Netlfix and Amazon Prime just before an HDR video plays it flashes and plays very washed out color palette. I rebooted the Roku and uninstalled both apps and reinstalled and still have the same issue. I bought a new model Roku Premiere hoping this would fix the issue and it did not. The HDR content plays fine on the Native Samsung Netflix and Amazon Prime TV apps so this is clearly a Roku issue. Is there any fixes currently for this.
Same exact issue on my Samsung KS8000. HDR is always dirty, dark and washed out on the roku. Across multiple apps too. Native apps always looks fine, in fact great in HDR. Like was said in this post, definitely a Roku issue not a TV issue. Looking at Amazon Fire stick because of this.