A little PSA for those who are playing their Switch 2 on a 4k OLED TV. Because the HDR setup is apparently not done very well in the Switch menu and there's a setting I didn't even know about that could be throwing it way off.
First step is to go into your TV Settings > Brightness > Dynamic Tone Mapping > HGIG.
Unless you've done it before, it is very likely just set to "On", but you have to change it to "HGIG". This essentially stops the TV from trying to override the HDR setting that your console will be sending to your TV. (And the setting will only be visible with your Switch turned on.)
Then, on your Switch, go to System Settings > Display > Adjust HDR. You'll have to click up or down until you see the gray sun icon on the left but not on the right.
And then in the next page, you'll see a sample image of Super Mario Wonder. Here, you have you press Y to adjust brightness (which is easy to miss), and I recommend turning that down several notches. The overall image will look a little dimmer, but the colors will look a bit deeper and pop a little more. (Otherwise if the overall brightness is too high, colors can wash out.) I set it just around 1/3 of the way from the left.
Finally, make sure to only enable HDR for HDR compatible games, NOT for all games. (HDR will basically ruin non-HDR games.)