If you have an XBox Series X or S and have had problems with dark Netflix picture, this may apply.
Playing around with HDR and Dolby Vision settings on XBox this evening to chase down a problem with occasional dark picture issues on Netflix. Found out that enabling Dolby Vision made any DV-encoded Netflix show really dark, sometimes unwatchably so. Disabled DV but left HDR enabled and everything seems fine. After all the testing I remenbered I'd had the same issue with a couple of DV-encoded video games, too. Doesn't seem to affect YouTube, Prime Video, or Disney+.
Brad