I'm having precisely the same problem. Will let you know if I make any progress. The issue seems to be related to code signatures. The error message shows that Xcode found @rpath/ArgumentParser.framework/Versions/A/ArgumentParser (@rpath in this case points to the Debug directory of my app) but finds it with a signature other than mine. Well, of course that will be true; I didn't sign the package because someone else wrote it.