SUMMARY
Using kwin and nvidia combo results in a limited color space.

STEPS TO REPRODUCE
1. Use KDE with Nvidia proprietary drivers

OBSERVED RESULT
Using KDE + Nvidia combo:
* No difference in here (on chrome): https://www.wide-gamut.com/test/image-sdr where sRGB and P3 look identical.
* `kscreen-doctor -o` results in `Color resolution: unknown`
* GUI System Settings -> Display Configuration does NOT HAVE `Limit color resolution to`

Using intel iGPU via a laptop:
* introduces color differences https://www.wide-gamut.com/test/image-sdr
* screen is a bit dimmer under the same brightness level (due to sRGB being sRGB and an extra `kick` left for wider color spaces)
* `kscreen-doctor -o` results in `Color resolution: automatic (10), range: [6; 12] bits per color`
* Display settings do HAVE `Limit color resolution to`

I did test with a couple of different screens (i.e., a monitor and a projector) => same outcome.

EXPECTED RESULT
Kwin + nvidia acts same as on the laptop with intel iGPU.


SOFTWARE/OS VERSIONS
Operating System: Kubuntu 25.10
KDE Plasma Version: 6.5.5
KDE Frameworks Version: 6.20.0
Qt Version: 6.9.2
Kernel Version: 6.17.0-14-generic (64-bit)
Graphics Platform: Wayland
Processors: 24 × AMD Ryzen 9 9900X 12-Core Processor
Memory: 69 GB of RAM (67.0 GB usable)
Graphics Processor: NVIDIA GeForce RTX 5070 Ti


ADDITIONAL INFORMATION
Nvidia drivers: 580.126.09