External Display Not Working

Dear community,

My new Thinkpad P15 Gen 2 (iGPU + dGPU) does not recognize external display (Thinkvision T34w).

  • Installed Q4.1rc2 and applied all the latest dom0 updates up to time of writing.
  • Tested both HDMI and USB-C cables
  • Plugging in external monitor immediately launches Qubes Display Manager (but no monitors except built in display are shown as available).
  • xrandr shows only built-in monitor
  • Also fails if monitor is plugged in before boot - does not matter.

The same monitor is compatible and works perfect with older Thinkpad P51 (Intel iGPU+ nVidia dGPU) tested on Qubes 4.0 - both USBC & HDMI.

Also the same monitor is compatible with Librem 14 tested on Qubes 4.1rc2 via HDMI only.

How should i troubleshoot this?

I am having similar issues at boot time only. Laptop Thinkpad X13 AMD gen2.
If I connect the laptop to monitor at boot time, both USB keyboard connected to monitor and laptop original keyboard will not respond to disk password. Only option is to power cycle.

After booting it is working monitor is working, FYI, I do not have dGPU.

I think your issue may be different to the one that OP is having as you’ve only got an iGPU on your model.

Often when I boot, I’ll get garbled text on the Qubes Linux FDE password screen or it won’t show the characters being typed, but if I type them anyway and hit enter it’ll go on to the Linux user login screen.

If you press the “Esc” key while at the FDE password screen you should be presented with a CLI prompt requesting your password. Does typing using the laptop’s onboard work at the CLI password prompt?