Chrome HDR is undoubtedly one of the most valued functions in the Google browser by users who enjoy the highest video quality. And the same goes for Edge, the Microsoft browser, which also has the ability to play this content properly (actually, it also uses Chrome HDR from its jump to Chromium). Remember that HDR (High Dynamic Range) add two bits to the eight that are used to define the color of each point and that is usually used, both in photography and video, to improve the representation of areas with quite different levels of light within the same frame.
For some time now, the main online video platforms, as well as device manufacturers (both televisions and monitors) have been betting on this technology. The first supporting HDR content in them, and the seconds making compatible displays with the nearly 1 billion colors that can be generated with the 10 bits. The third leg of the bank, of course, is the software to watch such videos, which is what Google offers with Chrome HDR and Microsoft with Edge Chromium. One leg is missing for four, of course, and in this case it is the operating system of the device that is used to view the content.
And this is where the bad news arrives, since according to some users on Reddit, both Chrome HDR users (in Chrome 81 and later) and Edge Chromium users in Windows 10 have verified that HDR content brightness level is displayed incorrectly when modifying Windows HD settings, a function of the operating system. More specifically, the problem occurs when accessing Windows HD Color settings and trying to modify the “SDR Content Appearance” setting with a slider.
As you have already deduced, eThis function is responsible for managing the SDR content, standard dynamic range (normal, go), in the context of a device with HDR capability. However, this which should not affect Chrome HDR at all is causing YouTube videos in this format to not be viewed correctly. Now the question is whether this problem is also related to May Update 2020, the last and not too successful update of the Microsoft operating system.
The good news is that those responsible for Chromium, that is, the engine used by both Google Chrome and Microsoft Edge, have already acknowledged receipt of the problem and claim to be working on a solution for the same. «Chrome HDR is affected by Windows SDR’s brightness settings. It seems to compound making all HDR videos look blown out unless Windows SDR Setting is turned all the way down, making the rest of desktop unusable«. So, therefore, it is only a matter of time (and hopefully the minimum possible) to be able to enjoy YouTube HDR content again in Windows 10.