Fixed Ubuntu screen brightness not working. Install Brightness Controller, Ubuntu brightness application that is used to control brightness of your primary and secondary display in Linux. It is a software based dimmer.
It allows you to control the brightness of your monitor to a better extent. For example, laptop’s monitor brightness can be controlled using hardware keys at discrete values, such as 20%, 40%, 60%, … 100%. Brightness Controller allows you to change the brightness to a better degree of control, ranging from 1% to 100%! It should be mentioned that it changes the present brightness value set via hardware control of your monitor. For example, if you set your Monitor’s brightness to 50% using hardware buttons, then that will be the 100% value in Brightness controller.
Run the following commands in Terminal to install Brightness Controller via Ubuntu:
sudo add-apt-repository ppa:apandada1/brightness-controller
sudo apt-get update
sudo apt-get install brightness-controller