Are there any good blue light filters that can be used in Ubuntu MATE 21.04?
Have you tried 'Red Shift'? By default it should be installed in Applications --> Accessories --> Red Shift. Here's some information on it. If not the answer you're looking for it might be a place to start.
Read the article, it tells you how to give the system your latitude and longitude.
Tried everything in it, still not working.
OKay, let's try this in stages....
First do you have geoclue-2.0 installed? If not, then:
sudo apt-get install geoclue-2.0
If you get a message saying that it is already the latest version, then go back to the link I gave you earlier, get the sample configuration:
In terminal open pluma and the config file by typing:
Paste in the contents of the sample configuration. Find where it says:
Then in a web browser search your location and latitude and longitude. Take the numbers which come up and plug them in the sample configuration open in Pluma. Once you've added the latitude and Longitude, save the file and close Pluma. Then try opening the application again. It should show up in the indicator section.
I use redshift on Manjaro-Mate and same times i have the same problem as @qwertyuiopasdfghjklz.
The solution was installing geoclue-2.0 (via extra).
Different distros same solution !
Personally, for some reason I have never had much luck with geoclue finding my location.
I just look up my cities latitude and longitude, set my defaults in pluma, put it in my user .config folder and keep a backup copy for the next time I do a fresh install.
You might find this approach useful - I use it: