(Copy of my Lenovo forum post)
ThinkPad X1 Yoga Gen 7 (12th Gen Intel) BIOS and TB firmware fully updated. ThinkPad Universal TB4 Dock firmware fully updated. Ubuntu 22.04.1 LTS _installed_ and fully updated. LAN cable plugged into dock.
Ubuntu boots to login screen. LAN LED on connected switch is ON and things seem OK. When I log in LAN LED flashes and goes out. Mouse and keyboard become unresponsive quickly. I am sometimes able to try to launch FF or select shutdown but that's as far as it gets. Nothing happens except eventually for the shutdown option the desktop wallpaper disappears and is replaced with a black screen and flashing cursor. Forced power off via long button press is the only option.
On reboot to Windows LAN LED is not on, and connection is not restored until I dis/reconnect the dock. If I boot Ubuntu on the AC brick or on a Lenovo USB-C Mini Dock + LAN issue doesn't happen. LAN works on mini dock. If I boot with TB4 dock but no LAN cable, no issue. Wifi works. My TP X1 Yoga Gen 6 with Ubuntu 21.04.1 LTS booted is fine on the TB4 dock + LAN.
Attaching syslog. I log in at ~ 17:41:25. Logs include failed session and subsequent session on AC brick when I extracted the logs.
This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:
apport-collect 1987170
and then change the status of the bug to 'Confirmed'.
If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.
This change has been made by an automated script, maintained by the Ubuntu Kernel Team.