brightnessctl VS Clight

Make sure you've the correct /usr/lib/udev/rules.d rule.

brightnessctl that works well! https://github.com/Hummer12007/brightnessctl

Tip: brightnessctl is a program that does the same thing and doesn't need udev rules.

try brightnessctl (present in official repos)

I think I used this one, seemed to work for me

The problem was with udev rules. It was not there for some reason

brightnessctl should be used without root permisions. Check how you can do it th the README: https://github.com/Hummer12007/brightnessctl. Depending on how you installed the package the udev rules could be already installed but you also need your user in the video group.

brightnessctl - This program allows you to read and control device brightness.

There is also Clight (https://github.com/FedeDP/Clight) if you want automatic backlight adjusting given ambient brightness. It supports external monitors through ddcutil C library and has many more features to offer.

Here are two suggestions from the Arch Wiki, try Clight or macbook-lighter. Clight looks to be continuously maintained, so I'd try that one first.

Clight can do that. See the config file.

Installed light, clight, clightd and acpilight

If you're using a laptop screen, there's Clight, which can turn your webcam into an ambient light sensor.

Clight is a lightweight C user daemon utility program that turns your webcam into a light sensor which it depends on to automatically adjust your screen’s display based on ambient light. Just like Redshift, Clight can manipulate the temperature of your screen and it derived inspiration from Calise.

Check out Clight. There's also a GUI for it.

The only downside to Clight? You need to build not only Clight and Clightd from source, but also 2 dependencies (libmodule and ddcutil), as well as the Clight-GUI if you want to use it. That is, unless you use Arch Linux / Manjaro (there are AUR packages available), NixOS, Exherbo or Void Linux, for which there are packages available.