We had a similar problem. There does not appear to be any purpose for a lot of the stuff that Qt Creator piles into the ".app" file, and it interferes with Apple Notarization.
We solved the problem by simply creating a command file that deletes the conflicting files:
# Clean out detritus that prevents notarization cd foo.app find . -name "*.h" -delete find . -name "*.prl" -delete find . -name "*.cstemp" -delete find . -name "Headers" -delete find ./ -name "*_debug" -delete