Install brightnessctl by entering the following commands in the terminal:
sudo apt update sudo apt install brightnessctl
Description:
Control backlight brightness
brightnessctl is a small utility to control the brightness of a screen's backlight. . This package contains the brightnessctl utility itself.
Homepage: https://github.com/Hummer12007/brightnessctl
Version: 0.3.1-1
Section: universe/misc