Copilot lied and made up things twice about this...

aboutToBeDestroyed exists, but it is an attribute of the
context, not the widget. And it must be connected after initializeGL
(where the context comes into existence), not earlier.

The signal is used for re-parenting, so normal exit does not fire
the signal.

Author: HinTak

openglwidget_abouttobedestroyed.py

@@ -6,20 +6,20 @@
 class MyOpenGLWidget(QOpenGLWidget):
     def __init__(self, parent=None):
         super().__init__(parent)
-        # Connect the aboutToBeDestroyed signal to your cleanup slot
-        #self.aboutToBeDestroyed.connect(self.cleanupGL)
 
-    #@pyqtSlot()
-    #def cleanupGL(self):
-    #    # This will be called just before the GL context is destroyed
-    #    print("OpenGL context is about to be destroyed. Clean up GPU resources here.")
+    @pyqtSlot()
+    def cleanupGL(self):
+        # This will be called just before the GL context is destroyed
+        print("OpenGL context is about to be destroyed. Clean up GPU resources here.")
 
     def closeEvent(self, event):
         print("Widget is about to be destroyed")
         super().closeEvent(event)
 
     def initializeGL(self):
         print("initializeGL: OpenGL context created.")
+        # Connect the aboutToBeDestroyed signal to your cleanup slot
+        self.context().aboutToBeDestroyed.connect(self.cleanupGL)
 
     def resizeGL(self, w, h):
         print(f"resizeGL: {w}x{h}")