QFileDialog setSizeGripEnabled(False) has no effect.

#include "mainwindow.h"

#include <QApplication>
#include <QFileDialog>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    QFileDialog f;

    f.setSizeGripEnabled(false);
    w.setCentralWidget(&f);
    w.show();
    return a.exec();
}

from PySide6.QtWidgets import QApplication,  QFileDialog

import sys

def main():
    app = QApplication(sys.argv) if QApplication.instance() is None else QApplication.instance()
    
    fileDialog = QFileDialog()
    fileDialog.setSizeGripEnabled(False)
    fileDialog.exec()
    sys.exit(app.exec())
if __name__ == "__main__":
    main()