There's also Monitorian for Windows: https://github.com/emoacht/Monitorian
And for a more advanced feature set, ClickMonitorDDC.
Sadly it is no longer hosted by the company where the developer worked. I mailed them, asking where the dev went or if they could put me in contact with him so he could release the source code. Regretfully I never got a response.
Fortunately there’s an open source alternative called TwinkleTray: https://github.com/xanderfrangos/twinkle-tray
Someone determined enough could add adaptive brightness to it. You can even use Lunar’s wireless ambient light sensor [1] for that as it’s simply sending lux values through Server Sent Events [2]
[1] https://lunar.fyi/sensor
[2] https://github.com/alin23/lunarsensor