I’m also experiencing the same issue when watching this particular YouTube video . However, when I downloaded the 4K HDR (WebM) video and played it in VLC, I didn’t encounter any problems, regardless of hardware acceleration or brightness settings. I’m unsure if the downloaded video is truly HDR, but it seems to work fine.
I played the video on ReVanced Extended without HDR and it seemed fine. I couldn’t play it with HDR because ReVanced has some issues with HDR playback.