When I first plugged in my ThinkPad OneLink Pro Dock, with an external monitor (really a Samsung TV) connected via a Displayport-to-HDMI cable, and it worked. My computer is an X1 Carbon 3rd gen.

Then two days later the external display stopped working, with no changes by me other than typical Ubuntu updates. The monitor says there is no signal. Ubuntu 21.10 (Wayland) now shows it as an "unknown display" with 640x480 resolution. If I pull the video cable from the dock (or the TV) it goes away, leaving the built-in as the only display.

This dock is supposed to be "driver free pass through dual video", so don't think it's DisplayLink drivers, but I tried installing them anyway, no luck. It's so weird that it worked once and stopped. Direct HDMI-to-HDMI cable between the computer and monitor (bypassing the dock) works fine and has for a long time. So that's a decent workaround, but figured I'd ask in case anyone has ideas to get it working; and I wanted to post just as a record in case anyone else has a similar issue.

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1 Answer

This seems to have been caused by failure of the DVI to HDMI cable. Got another one, all better now.

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