You are presenting a linker error, so you have not yet built the program.

The SOURCES entry in the top-level PRO file is not useful. The subdirs project type does not build any code itself.
The config folder contains nothing to be built and should not be listed in the subdirs project. No PRO file is needed in that folder.
In order to build Presenter you need to tell it where to find the built Utilities library (LIBS) and ensure Utilities is built first (Use CONFIG += ordered with subdirs).

When I fix those things the program builds.