Reducing brightness makes black/near black *brighter* and washed out

Kubuntu KDE Plasma Wayland (problem occurs on X11) with OLED HDR screen (Razer Blade 15 (2020))

As per the title, the screen gets significantly brighter going from 100% to 80% birther, and black/near black colors shift to a washed out dark grey. If using a dark mode/theme, this makes the display much brighter overall. From ~80% down to ~0% the overal brightness goes down but stays washed out.

I’ve tried using the .icm file from original windows that came with the Razer Blade, and setting RGB range to “full” and using colord-brightness (which seg faults).

Really liking KDE/Kubuntu, but this is very annoying.

Seems like it should be a simple matter: On an HDR OLED screen, just scale all pixel RGB values by the brightness setting. Windows seems to manage this just fine.

Any help?

Note: problem still exists if I try Plasma(X11) instead of Plasma(Wayland). [Edit: same problem on “Weston”]