https://doc.qt.io/qt-6/qdialog.html#modal-dialogs says: "The most common way to display a modal dialog is to call its exec() function." However, https://doc.qt.io/qt-6/qdialog.html#exec has a note that says "Avoid using this function; instead, use open()."

https://doc.qt.io/qt-6/qdialog.html#open refers back to https://doc.qt.io/qt-6/qdialog.html#modal-dialogs. Which does not mention `open()`, but `show()`, and goes on to say: "If you use show() and setModal(true) together to perform a long operation, you must call QCoreApplication::processEvents()". However, the documentation of the latter says: "Use of this function is discouraged."

So there seems to be no way to open a modal dialog for a long operation that is not deprecated.