Yes, in my experience, most monitors do accept DDC commands even if the video signal comes from another input as long as the other input keeps the line busy.
For example, on the Pi this was not possible in past, we had to wait for the vc4-kms-v3d GPU driver to get this functionality. Thankfully it’s beta version coincided with the M1 release :)
There’s no DDC dial available, but it’s something I tried doing in the past using an ESP32 that gets Power-over-HDMI [1] and sends DDC through the I2C wires of the HDMI cable [2]
Unfortunately I had to put that on hold as I started a Mac app studio [3] which took most of my time away. (and I also realized I don’t have the means to sell and distribute a hardware project)
For example, on the Pi this was not possible in past, we had to wait for the vc4-kms-v3d GPU driver to get this functionality. Thankfully it’s beta version coincided with the M1 release :)
There’s no DDC dial available, but it’s something I tried doing in the past using an ESP32 that gets Power-over-HDMI [1] and sends DDC through the I2C wires of the HDMI cable [2]
Unfortunately I had to put that on hold as I started a Mac app studio [3] which took most of my time away. (and I also realized I don’t have the means to sell and distribute a hardware project)
[1] https://www.hdmi.org/spec21sub/cablepower
[2] https://github.com/tttttx2/ddcvcp
[3] https://lowtechguys.com/