Hi Mark,
Thank you for the input, the issue was resolved last Sunday with someone’s help from the NVIDIA Developer Forum (Ubuntu 18.04 NVIDIA driver not loaded after GCC update - #9 by generix - Linux - NVIDIA Developer Forums), I had to set NVreg_ModifyDeviceFiles=1 in /etc/modprobe.d/50_nvidia.conf, update initramfs, and reboot, and now nvidia-smi is working correctly.
The cause might be what you described that with the GCC version, it all started when the user updated GCC from the default 7.5 to 9.4.
Thanks,