When building Qt statically any instance "import QtQuick.Window" call fails on startup.
The Window import has been moved to QtQuick, so just removing the line makes the application run.
It should be reproducible with any Qt Quick Controls 2 example which uses ComboBox for instance, since this has such an import.
But note that building qt quick controls 2 in its source tree does not work because of
QTBUG-86949, so to test, make an example in a directory outside the Qt source tree.