main.py

from PyQt6.QtWidgets import QWidget, \
                            QCheckBox, \
                            QApplication
from PyQt6.QtCore import Qt
import sys

class Example(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        cb = QCheckBox('Show title', self)
        cb.move(20, 20)
        cb.toggle()
        cb.stateChanged.connect(self.changeTitle)

        self.setGeometry(300, 300, 350, 250)
        self.setWindowTitle('QCheckBox')
        self.show()

    def changeTitle(self, state):
        if state == Qt.CheckState.Checked.value:
            self.setWindowTitle('QCheckBox')
        else:
            self.setWindowTitle(' ')

def main():
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec())

if __name__ == '__main__':
    main()