Following up/“answering” on my previous post about my monitor issues with the Kensington SD5780T dock and monitor connected to it over HDMI:
I finally got my hands on a second, Apple, TB4 cable. Just replacing the host/dock cable with this Apple cable didn’t fix the issue:
[FW]---(Apple TB4 cable)---[dock]---(HDMI cable)---[monitor]
So I switched back to the Kensington-supplied TB4 cable.
Then, on a whim since I now have a second TB4 cable around I used one of the dock’s TB outputs to connect to the monitor’s USB-C (DP alt mode) input instead of HDMI:
[FW]---(Kensington TB4 cable)---[dock]---(Apple TB4 cable)---[monitor]
and to some surprise the monitor (EDID) gets detected correctly and everything (display-wise) works.
This does make the Linux kworker issue, or rather its workaround of toggling power to the dock, have more of an “impact” with various windows scurrying off to the laptop monitor, as expected.
Anyway, for extra kicks I also tried:
[FW]---(Apple TB4 cable)---[dock]---(Kensington TB4 cable)---[monitor]
And that, consistently, results in a new failure mode: The monitor is detected but only at 30Hz. Not enough bandwidth?
Anyway, the Kensington cable seems to be at least part of the problem - on the AMD USB4 host - The same first/original topology above still works with many other laptops including a gen11 Intel FW.