OK, I think you’ll need 3 network interfaces in your Nethserver, one for the 10.0.x.x network, one for the internal vlanned network and one for the WAN 192.168.xxx.xxx network. This makes Nethserver to your router to manage traffic from one network to another.
Network roles, 2 x green, 1 x red:
This worked for me in a quick VM test:
Choose green role for the internal LANs:
Hope I understood you right…