I recently come across an issue that the night light in Pop! OS runs few seconds then get back to the bluelight even though it's ON and set to sunrise to sunrise, the easy solution that I found to install gammastep
Use gammastep:
sudo apt install gammastep
gammastep -O 3000 # Test (3000K = warm, higher value more bluelight)
to learn more about the features run:
gammastep -h
good luck :)
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