Please disregard swapnali01's unhelpful answer which has nothing to do with the issue.
All Intel macs supported DDC/CI, both with AMD and Intel GPUs (or even nVidia when that was available). The lack of DDC/CI support breaks several popular third party utilities (like MonitorControl or Lunar.fyi and others) designed to control the brightness and volume level of most modern external displays. It also breaks and cripples apps designed by display manufacturers specifically for Macs to control external displays (like BenQ's Display Pilot or LG's Screen Manager).
For more information on the issue:
https://github.com/kfix/ddcctl/issues/86https://github.com/MonitorControl/MonitorControl/issues/323https://github.com/alin23/Lunar/issues/210#issuecomment-752405561The arbitrary way Apple sometimes just leaves out important features from its products is alarming. It hurts the ecosystem, creates confusion and uncertainty. 6 months has passed since M1 was introduced and still there is no resolution to this issue. But the missing DDC/CI implementation is just the tip of the iceberg, external display support is still a mess in general (user forums are full of complaints about resolution issues, washed out colors - M1 Macs switch to limited RGB range for no good reason - on LG displays via DisplayPort over USB-C, broken HDR support etc). It's a shame!
