Then you definitely have some settings wrong.

Make sure the monitor is set to HDR mode (in the monitor’s built-in settings), and the OS is set to treat the monitor as HDR. Depending on the OS there may be other things to play with. E.g. I was getting the issue with things looking washed out after the latest bazzite update until I manually installed VK_HDR_LAYER

Here is a site I usually use to test that HDR is working correctly: https://www.wide-gamut.com/test (you may need a chrome based browser, Firefox doesn’t always render it correctly)

It always makes the picture look all washed out and desaturated

This is a typical symptom when part of the HDR pipeline is working but not all of it. The HDR image is getting (poorly) converted to SDR before it’s being displayed.

Actual HDR is richer colors than SDR. Note that you basically need an OLED monitor to display it properly. On most LCD monitors that advertise “HDR” support, it won’t look very different.

I’ve got HDR working with an Nvidia card on bazzite but the current workaround means I can’t use HDR and Steam Input at the same time. This is using the gnome variant. I think the situation may be better with kde.