Q. How do I add additional drivers to a Nano Server instance?
A. To add drivers to an existing Nano Server instance the pnputil.exe can be leveraged with the /add-driver switch. You should have a folder with the required drivers in it, e.g. c:\drivers then use:
pnputil.exe /add-driver c:\drivers\*.inf /subdirs /install
You cannot perform an online installation of non-PNP drivers. To install drivers offline utilize DISM or DISM PowerShell in the same way other updates etc are installed.