Working vs not working(?!)

[ArchieLinux]

Greetings! brightnessctl has shown itself to be the instant solution to regaining control over my native monitor's brightness [via dimmer key (F1) and brighter key (F2)] on my 2019 iMac desktop. I access it easily through keybindings I added within my wmi3 config file.

PROBLEM: I cannot get my 2011 MacBookPro to respond at all ... nor can I get my Dell OptiPlex 7200 to respond ... yet all three are running identical setups, i.e., the same Zen kernel 6.1.6, EndeavourOS, i3, etc.

The difference I detect is that the device 'acpi_video0' is listed via brightnessctl -l on the iMac but there is nothing comparable on the other two platforms (other led devices but not a monitor). In short, I can't seem to find the monitor(s) in the device listings as shown by brightnessctl.

Any thoughts on why? ... and how I might get brightnessctl to recognize the monitor device equivalents on the others?

[Hummer12007]

External monitors should work with the DDCI module, but in practice it doesn't work (see #105).