Linker error for non exported module

Linker errors even tho you have everything linked

If you get linker errors for a type and you've checked all the usual suspects (using UEngineCamerasSubsystem as an example)

✅ is the module included in the build.cs

✅ is the plugin activated in project settings (only needed for runtime only plugins but nonetheless)

✅ #include is correct

Check that the module is actually exported

This was the case for UEngineCamerasSubsystem that the class I was trying to use didn't have a DLL export macro specified

Fix by adding DLL export macro

Find the name of the plugin from the module.cpp file (or build.cs file)

The macro will be the <name>_API so in this case ENGINECAMERAS_API which you can validate by either jumping to declaration in the generated code

Once you've added the DLL export macro you can freely use the type.

Note: you can also just export the functions or parts of the class you need rather than the entire class by adding the macro to them instead of the overall class