If your physical keys are broken or you are using a desktop keyboard that doesn't support it, use these shortcuts:
A "Display Adapter" or "PnP Monitor" update in Device Manager usually fixes it. brightness key on keyboard
If you are tired of holding the Fn key, you can often reverse this behavior in your BIOS settings or by pressing Fn + Esc (if your keyboard has an Fn Lock icon on the Escape key). If your physical keys are broken or you
Apple keyboards are consistent and intuitive: brightness key on keyboard
The method of pressing these keys depends on your specific keyboard hardware.