I did
dpkg -l | grep nvidia
dpkg -l | grep nvidia-driver
to get lists of nvidia related drivers. The one by one did
apt purge [packagename]
(sometimes had to change the order of which package was being removed)
then did
apt autoclean
apt autoremove
...to clean up any dependencies that were hanging around
re-ran
dpkg -l | grep nvidia
dpkg -l | grep nvidia-driver
to make sure list was empty then rebooted then followed
https://wiki.debian.org/NvidiaGraphicsDrivers#Version_535.183.01-1
to reinstall drivers.
Then did a clean install of comfyUI
Everything seems to be working again.