OpenGL under QML not rendering properly

[KeenJackdaw]

I'm running the OpenGLUnderQML example under MACOS.

It should generate a window like this

But it actually rendered a white window.
After some test I found that if I add these line to qtquickcontrols2.conf, I got the right ouput.

[Controls]
Style=Material
[Material]
Theme=Dark

[KeenJackdaw]

The style must be Material and the theme must be dark, otherwise it renders a white window again.