Okay, I used TimeShift to load an image from before the update and tried again.
I followed the steps as listed here: [Stable Update] 2020-09-08 - Kernels, Mesa, Browsers, KDE Apps 20.08.1, Systemd, LibreOffice 7.0.1, Deepin
Specifically, I did the following:
pamac remove nvidia-440xx-utils linux414-nvidia-440xx linux58-nvidia-440xx cuda
mhwd --install pci nvidia-450xx
Although the command says “successfully installed video-nvidia-450xx” it is preceded by the following warnings and errors:
> WARNING: Possibly missing firmware for module: xhci_pci
> rmmod: ERROR: could not remove 'nouveau': No such file or directory
> rmmod: ERROR: could not remove module nouveau: No such file or directory
> rmmod: ERROR: could not remove 'ttm': No such file or directory
> rmmod: ERROR: could not remove module ttm: No such file or directory
> rmmod: ERROR: could not remove 'drm_kms_helper': Resource temporarily unavailable
> rmmod: ERROR: could not remove module drm_kms_helper: Resource temporarily unavailable
> rmmod: ERROR: could not remove 'drm': Resource temporarily unavailable
> rmmod: ERROR: could not remove module drm: Resource temporarily unavailable
> modprobe: ERROR: could not insert 'nvidia': Exec format error
> xorg configuration file: '/etc/X11/mhwd.d/nvidia.conf'
> modprobe: ERROR: could not insert 'nvidia_drm': Exec format error
I reboot and I get the light display manager error as before. I then removed the 450 driver and re-installed the 440 driver but I get the same error messages and the light display manager error persists.