In a non-flat network it is imperative to use existing mechanisms for coherently distribution network configuration to the nodes.
Static routes for internal networks come in handy if using e.g. OpenVPN on machines and still wanting to access services in other internal networks.
Static routes are best distributed using DHCP, eg. option 121 (classless-static-route).
macOS honors this option, Linux does, even Windows!
Osmc should be no exception to this!
Sure, it is possible to make a local configuration, even using the openvpn config file. That is not the point here. This file would need to be updated every time when the Osmc box is moved to a different internal network. That is not suitable and not the response I am looking for.
Why not just use a dhcp client that honors the pertinent options?