BTW: I have now pushed a fix to master that converts all QFileDialogs to use QFileDialog::DontUseNativeDialog just for macOS (and for Linux where it was set that way before).
This should workaround a number of ignored and closed as too old Qt bugs related to QFileDialog on macOS that report that the native versions of QFileDialogs do not always properly exit from exec().
The reports were all basically ignored by Qt but made it clear that this seems to hit only some machines and some users and even then not consistently.
My guess is that this is a structure alignment or signal issue issue but no one at Qt has bothered to look more closely.
For reference see here are many of the related Qt bug reports for QFileDialog and macOS:
https://bugreports.qt.io/browse/QTBUG-57009
https://bugreports.qt.io/browse/QTBUG-66138
https://bugreports.qt.io/browse/QTBUG-69437
https://bugreports.qt.io/browse/QTBUG-71234
https://bugreports.qt.io/browse/QTBUG-76563