initializeOpenGLFunctions returning false for 2.0/2.1 since macOS BigSur

Hi!

We started getting reports of our OpenGL renderings not working anymore under newer macOSes. To confirm, I upgraded my developer machine (Intel) from Catalina to BigSur (the latest it can install).

And our code indeed now fails to initialize OpenGL. We have a class that inherits from QOpenGLFunctions_2_0 (I also tested with 2_1) since we use legacy functions. It calls initializeOpenGLFunctions() which suddenly returns false. Everything was fine under macOS Catalina.

From what I read, 2.1 and 4.1 Core should still be supported on macOS. Is there any way to debug why the initialization returns false?

If I continue rendering, any GL call will crash the program with a segfault (since of course the function wrapper is not initialized).

Currently, I am using 5.15.5_1 from homebrew but I already downloaded 5.15.2 from the official installer to double-check.

Thanks for any help or suggestions.

STEPS TO REPRODUCE:

Use your helloGL2 example and additionally link to Qt5::WebEngineWidgets. It will segfault right away.

I think inheriting from QOpenGLFunctions_2_0 instead of the default QOpenGLFunctions is not even necessary. The link to WebEngineWidgets (in my case via CMake target_link_libraries) seems to be the culprit.