System tray menu not created Ubuntu and Windows 10

from PySide6.QtWidgets import QApplication, QWidget, QSystemTrayIcon, QMenu, \
    QMessageBox, QSizePolicy, QPushButton, QHBoxLayout
from PySide6.QtGui import QIcon, QAction
import sys

class Application(QApplication):
    def __init__(self, args):
        super().__init__(args)
        
        # Keep application running when all windows are closed
        self.setQuitOnLastWindowClosed(False)
  
        # Create the menu
        menu = QMenu()

        # Create quit button
        btn_quit = QAction('Quit')
        btn_quit.triggered.connect(QApplication.quit)

        # Add buttons to menu
        menu.addAction(btn_quit)

        # Create system tray icon with menu
        # https://doc.qt.io/qtforpython/PySide6/QtWidgets/QSystemTrayIcon.html
        system_tray = QSystemTrayIcon()

        # Set system tray icon (make sure path is correct, otherwise icon is not created)
        system_tray.setIcon(QIcon("icon.png"))
        
        # Add the menu to the system tray
        system_tray.setContextMenu(menu)

        # Make system tray icon with menu visible
        system_tray.setVisible(True)

        # Show system tray
        system_tray.show()
        
        # Workaround to place the loop here
        # sys.exit(self.exec())
        

def main():
    app = Application(sys.argv)
    
    # Ubuntu: Menu in system tray not created
    # Windows: Icon in system tray not created
    sys.exit(app.exec())


if __name__ == '__main__':
    main()