Do you mean that all client networks are the same number 192.168.4.0/24 ?
All devices have two ethernet ports. Port 1 is setup via dhcp and connect to the OpenVPN server.
Port 2 is set to a static IP 192.168.4.127. This is connected to a local network 192.168.4.0/24.
So all the devive clients have the same configuration.
Would it be possible to change the route dynamically?