My work laptop, an Intel Mac, displays to and controls brightness on the same monitor, but I've been using ddcctl with a trivial wrapper script much more than Lunar of late. (Kinda feel a little bad about that, what with the author of Lunar having taken the time to give me tech support on a weird corner case here on HN a while back.) Still going to buy a license and, if I can find a way, set up a recurring donation. This kind of work deserves support.
I completely understand when users go with something more simple like a CLI or MonitorControl. I do the same myself when I don’t really need the features of a complex app.
By the way, I’m not sure if I understood correctly but if you need an external ambient light sensor, Lunar supports that out of the box now: https://lunar.fyi/sensor
Currently I'm working with a sensor homebrewed from a reverse-biased LED with a Darlington-pair amplifier - not what anyone would call accurate, but precise enough to calibrate reliably over the range of light values to be found in my office as long as I keep direct sunlight off the transistors.
Between that, a Pi, ddcutil, and the currently unoccupied DisplayPort input on my monitor, I'm hoping to brew up something that'll serve well enough - not terribly optimistic on that given that the monitor seems to maintain per-input brightness settings, but worth a try at least. (Also, if it does work, I can add an encoder with a built-in button as a manual override.)
On the other hand, it seems likely that, by the time I find that approach to fail, Lunar on Mac mini will be able to do DDC via HDMI - I thought it'd take a year at least after the M1 arch came out for anyone even to get as far as you already have, but clearly I failed to reckon with your dedication to the effort!
