Compatibility With The Generator
generate_network_service.py does not special-case lwIP: the same keys apply—stackInitSourcePath, stackInitFunction, configFilePath, stackPath, and interfaces. When lwIP becomes the first use: true stack, the emitted headers will reference whatever function names and include paths you put in JSON.
A working build still requires real sources: for example AppLwIPStack.h implementing AppLwIPStackInit (or the name you configure), Ethernet/PPP managers, and middleware under Middleware/lwIP/ if your project uses that layout. Until those exist, generated code alone will not link.