I normally work with an external monitor connected by HDMI to a USB-C adapter. I also have a USB-C hub (Aukey CB-C48), tested working with another USB-C device.

The monitor works fine when connected directly to the computer by USB-C. But it is not detected when it is connected through the hub. udevadm monitor --environment --udev doesn't show an "add" event, and debug dmesg doesn't show anything responding to a hotplug event either. I tried an older VGA monitor through a different, VGA-to-USBC adaptor as well - same problem.

Is this a known limitation of USB-C hubs in general? Maybe the kernel's implementation? Or is there something I should look for when buying my next hub, to make this possible?

Here's a dmesg dump with drm.debug=0xe, where I:

  1. boot the machine (warm)
  2. plug in the hub
  3. plug in the monitor
  4. unplug the monitor
  5. attach a Pixel phone through the hub's powered port
  6. move the phone to one of the hub's unpowered ports.

This is probably related to (unanswered) Linux Mint - Not detecting monitor connected via USB-C to HDMI hub . I can't seem to find any other resources, though.

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