HDMI over USB-C

[qume]

I have a 2019 Macbook Air, and have tried three different USB-C to HDMI (or DisplayPort) adapters (passthrough / alt mode, not displaylink). None of them work, and regardless of whether they are plugged in or not, xrandr gives the following output:

DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)

All of these work under MacOS.

Running the latest Lunar kernel