XPS 13 with Displaylink 3100 non working HDMI ports

[AlbanRampon]

Thank you Yves.
There is no monitor detected, at all, by the chip in the dock.
For the DisplayPort monitor, I do see "hotplug" detection, then the monitor EDID being read and saved in the .edid file. However, there is nothing for any other head. That leads me to believe there is a fault in the hotplug detection hardware: no monitor is detected as getting plugged in, so the dock doesn't even try to read what's connected.
Is it a single dock behaving like that? If so, once you have verified it is not a cable fault, I would recommend contacting the manufacturer, Dell, to discuss a replacement. I suggest you copy this message so they don't waste time looking at the driver...