With your Nvidia GPU the newest version you can install is High Sierra. As Mojave, Catalina and Big Sur don't support your discrete GPU, as there are no NVIDIA Web Drivers available for the three newest version of macOS.
If you want to use a newer version of macOS you would need to replace the Nvidia card with a compatible AMD GPU.
I would suggest you make a Clone copy of your current macOS drive using Carbon Copy Cloner or SuperDuper, on a spare SSD or HDD. Then you can safely upgrade your current setup to High Sierra 10.13.6 without fear of messing up your working setup.
You may need to use the
nv_disable=1 boot argument and disable the
NvidiaWeb=true option when booting into High Sierra, as you will need to remove the current NVIDIA Web Drivers and install a new set, once you have High Sierra installed.
Actually you might be better served waiting till you have finished installing all the Security and Supplemental updates for High Sierra 10.13.6, before you reinstall the NVIDIA Web Drivers. As the drivers are version specific and you would end up upgrading the drivers numerous times till High Sierra was fully updated. This would mean your Nvidia GPU would work without full acceleration, while you were updating the system.
Alternative is to temporarily remove the Nvidia GPU. Use your Intel iGPU for the High Sierra updates, once they are finalised reinstall the Nvidia GPU and the version of the NVIDIA Web Drivers your system needs. If you have a look at the Downloads > Nvidia Drivers section on this site you will see what I mean about the 17 different versions of High Sierra 10.13.6 and the corresponding driver versions available -
https://www.tonymacx86.com/nvidia-drivers/