UPDATE - 3rd of March, 2023:

The following apps have support for control via the built-in HDMI port as of now:

• BetterDisplay - Built in HDMI ports of all Apple Silicon Macs (all versions of M1 and M2 chips) and also the 2018 Intel mini.
• Lunar - Built-in HDMI port of all Apple Silicon Macs (2018 Intel mini is not supported as of now)

MonitorControl is currently not updated, contributors are welcome to add a Pull Request with the required changes!

Note: all DDC feature is free with BetterDisplay, no limitations. DDC features are free for up to 100 adjustments/day with Lunar.

Explanation

The Macs listed in the question produce DisplayPort signal which is converted to HDMI via a special chip, the MCDP2900 DisplayPort 1.4a-to-HDMI 2.0b Converter.

This chip is able to receive Displayport 1.4 signal and convert it to HDMI 2.0. Apple uses the very same design for all of these Macs (hence the HDMI 2.0 limitation even on the newest Macs).

It seems, even though this chip is capable of performing I2C communication (which is required both for DDC control and retrieving display information - EDID), the communication is cut off at firmware level once the initial negotiation and download of the EDID is completed (alternatively, there might be a yet undiscovered method or service endpoint that would allow communication).

Since this seems to be a design decision on Apple's part and reprogramming this chip (if it is even possible) would require a properly signed firmware update from Apple, there is little chance that DDC control via HDMI will be resolved on newer Macs.

What can I do to change this situation?

You can contact Apple support and explain the situation and ask for the issue to be escalated to the engineers. You can also use the feedback assistant to add your voice.

Apple does not officially support or adhere to the DDC standard.