That’s a good lead, you have the same affected 300Hz panel. The main difference is that the .run installer you used is the latest, just released 460.73.01 driver while the repo driver is the older 460.56 driver. So this might be a bug that has been fixed in the latest driver.
The second difference is more subtle, depending on install the Ubuntu repo enables nvidia drm modesetting while the .run installer doesn’t.
Since you’re currently on the repo driver as it seems, please check:
run
grep nvidia /etc/modprobe.d/* /lib/modprobe.d/*
to find a file containing
options nvidia-drm modeset=1
and change 1 to 0
then run
sudo update-initramfs -u
and reboot.