In my case I saw this error after apt upgrade, and when I use recovery mode to reinstall the kernel(get version by
uname -r), I finally see some error of
Then, I check dpkg logs by
cat /var/log/dpkg.log | grep "xorg-xserver-video*"
and found that the earliest, working version of drivers are HWE versions(have "-hwe" in name), but now
dpkg -l | grep xorg-xserver-video shows that it is not installed(not in ii state, maybe removed by apt upgrade).
So I enable the network in recovery mode, installed them back(actually only
xorg-xserver-video-all-hwe-18.04), along with
xorg-xserver-input-all-hwe-18.04(drivers for input, as during the first successful boot I cannot use mouse nor keyboard), and reboot. Good again.
Thanks! I will never upgrade Intel or Nvidia drivers again. I guess that
lvmetad never worked from the beginning, but it does not prevent the OS from boot so we never saw it, until the failure of video driver brings us to the black screen, thus the wrong impression.