DDCBR is just a shell wrapper around ddcutil. It can be used to easily increment or decrement the brightness of a monitor.
Install ddcutil and clone this repo.
Follow ddccontrol's instructions.
Run ddcutil detect. Find your monitor in the list, and note the number after /dev/i2c-. Put this number in the BUS variable of ddcbr.sh.
Set the BASE_DIR variable to point to this repository.
Increase brightness by 10%:
./ddcbr.sh i
Decrease brightness by 10%:
./ddcbr.sh d
Keyboard shortcuts can be added to the window manager to call this script quickly.