There is no way to get DDC working on that port. It’s probably locked in the chip firmware.

All we can do is to provide software dimming using Gamma table alteration, or tell people to use the Thunderbolt ports instead.

Now I understand. There are two ways of dimming a screen. One is dimming the backlights in the display while the other is faking it via Gamma table alteration

They said use one of the Thunderbolt ports.

What problem? Is DDC not available?