I was always annoyed that I had to adjust brightness when switching from an IDE in dark mode to a bright web page. I was aware of Lumen https://github.com/anishathalye/lumen but didn't use it since it does not support external monitors.

Therefore, I built Lumos, which is heavily inspired by Lumen but adds support for external monitors. The DDC/CI part of the code is vendored from https://github.com/MonitorControl/MonitorControl. It really improved my experience and I almost never have to manually adjust brightness anymore. And it is open source so I wanted to share it here.