Bug 450029

SUMMARY
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I have i915 as a driver and hence having wide range of colors by default is definitely not for me. In KDE however there's a RGB range option in Display settings applet which, in my case should be manually set to Full (it's Automatic by default, which probably means "whatever driver decides in its wisdom"). The option can also be set by kscreen-doctor:
kscreen-doctor 'output.thescreenname.rgbrange.full

The option however keeps getting reset to Automatic after rebooting - it doesnt matter if I set it through the applet or kscreen-doctor.
Moreover, if I use libdrm's proptest to set properties of connectors so the option is set even in ttys, after starting KDE, I still get reverted to Automatic on it.

STEPS TO REPRODUCE
1. Have i915 & a screen connected with HDMI
2. Set RGB range to Full in Display settings
3. Reboot

OBSERVED RESULT
Washed colors.

EXPECTED RESULT
Colorful colors.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  Arch, latest
KDE Plasma Version: 5.24.0-1
KDE Frameworks Version: 5.90.0-1
Qt Version: 5.15.2+kde+r297-2

ADDITIONAL INFORMATION