K420 with 470.126.06 ubuntu 20.04 no graphics after updates

My ubuntu 20.04 with nvidia K420 and driver 470.129.06 will not show the login screen (only a black screen). It has been working for some years until I did a shutdown two days ago, possibly after some updates from apt, because I needed to relocate. There is a a single monitor attached to the dell precision tower model 7810, there has been no hardware changes. Linux boots OK and I can ssh into the box from the lan, and I cannot see any (EE) lines in the Xorg.0.log file. apt update reports that I’m up do date, as does apt upgrade. I reran nvidia-config and rebooted to try the new xorg.conf in /etc/X11 , no change in symptom. I will attach the nvidia-bug-report.sh output.
nvidia-bug-report.log.gz (315.7 KB)

It recovered. By itself. It is a dual-boot, and I booted to Win10 and did some updates there, then rebooted back to the ubuntu , and this time I got a login screen , and it all seems to be working. So I do not know the cause, but this question can be closed.