Python Qt Creator new project base class QMainWindow not showing dynamic form.ui

I've installed Qt Creator v9.0.1 on Ubuntu 22.04 / Windows 10 and try to create a new project which shows an empty frame and not the loaded form.ui:

Screenshot
Screencapture

Testcase:

File | New Project:
- Application (Qt for Python) | Window UI - Dynamic load:
  - PySide version: PySide6
  - Base class: QMainWindow

Default generated mainwindow.py:

# This Python file uses the following encoding: utf-8
import os
from pathlib import Path
import sys

from PySide6.QtWidgets import QApplication, QMainWindow
from PySide6.QtCore import QFile
from PySide6.QtUiTools import QUiLoader


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.load_ui()

    def load_ui(self):
        loader = QUiLoader()
        path = Path(__file__).resolve().parent / "form.ui"
        ui_file = QFile(path)
        ui_file.open(QFile.ReadOnly)
        loader.load(ui_file, self)
        ui_file.close()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    widget = MainWindow()
    widget.show()
    sys.exit(app.exec())

Default generated form.ui:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget"/>
  <widget class="QMenuBar" name="menubar"/>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

I expected the form.ui window size with menubar and statusbar instead of an empty small window. Same behavior on Windows and Ubuntu 22.04 Any suggestion?

Solution

Qt bug report: https://bugreports.qt.io/browse/QTCREATORBUG-25807.

Problem solved as this is a bug in Qt Creator when creating a New Project with dynamic load and QMainWindow base class:

# This Python file uses the following encoding: utf-8
import os
from pathlib import Path
import sys

from PySide6.QtWidgets import QApplication, QMainWindow
from PySide6.QtCore import QFile
from PySide6.QtUiTools import QUiLoader


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.load_ui()

    def load_ui(self):
        loader = QUiLoader()
        path = Path(__file__).resolve().parent / "form.ui"
        ui_file = QFile(path)
        ui_file.open(QFile.ReadOnly)

-        loader.load(ui_file, self)
+        widget = loader.load(ui_file, self)

        ui_file.close()

+        widget.show()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    widget = MainWindow()
-    # widget.show()
    sys.exit(app.exec())