I am looking for ways besides RDP to have employees connect to my work's internal network at another location so that they can VPN to one of their client's. The VPN connection only works from the internal network as their Sonicwall configuration is setup to allow it through IP's on my work's network.
Any third-party apps, Windows settings, or other suggestions are welcomed.
One suggestion by a friend was to use Cendio, an open source Linux remote desktop server.

I have a Windows Server 2016 Standard machine and several Windows 10 Pro machines