The GUI control appears and seems to work as intended.
- Tested that the default value of Perceptual is used when there is no value in ~/.config/gwenviewrc
- Tested that the value gets set in ~/.config/gwenviewrc
- Tested that removing the value in ~/.config/gwenviewrc reverts the GUI setting to Perceptual
Could not test that the setting makes a visual difference because none of my images changed appearance when I changed the intent to INTENT_RELATIVE_COLORIMETRIC--even when running Gwenview with that value hardcoded. If anyone can provide a file that will illustrate differences between any of the color rendering modes, that would help.