Hello,
Because your network card is not connected to a VPN, the option to use the default gateway on the remote network is missing. From the command you use, you can see that there is no available VPN connection, so it is displayed as empty. You need to have a VPN configuration file on your PC and then use the configuration file to connect to the VPN. It is recommended that you refer to the following link to configure VPN:
Connect to a VPN in Windows - Microsoft Support
I hope the above information is helpful to you.
Best Regards
Zunhui