For the list of options:
gammastep -h
I just installed & ran gammastep -h on my mini-PC:
gammastep -h
Usage: gammastep -l LAT:LON -t DAY:NIGHT [OPTIONS...]
Set color temperature of display according to time of day.
-h Display this help message
-v Increase logging verbosity
-q Decrease logging verbosity
-V Show program version
-b DAY:NIGHT Screen brightness to apply (between 0.1 and 1.0)
-c FILE Load settings from specified configuration file
-g R:G:B Additional gamma correction to apply
-l LAT:LON Your current location
-l PROVIDER Select provider for automatic location updates
(Type `list' to see available providers)
-m METHOD Method to use to set color temperature
(Type `list' to see available methods)
-o One shot mode (do not continuously adjust color temperature)
-O TEMP One shot manual mode (set color temperature)
-p Print mode (only print parameters and exit)
-P Reset existing gamma ramps before applying new color effect
-x Reset mode (remove adjustment from screen)
-r Disable fading between color temperatures
-t DAY:NIGHT Color temperature to set at daytime/night
The neutral temperature is 6500K. Using this value will not change the color
temperature of the display. Setting the color temperature to a value higher
than this results in more blue light, and setting a lower value will result in
more red light.
Default values:
Daytime temperature: 6500K
Night temperature: 4500K
Please report bugs to <https://gitlab.freedesktop.org/CameronNemo/gammastep/issues>
Although I will be uninstalling it now, as Plasma’s System Settings (Night Light, and Day-Night Cycle) fit my requirements.