QQuickWidget shows a blue rectangle when multisample anti-aliasing is enabled

I found this bug while trying to build our mixed Widget/QML desktop application against Qt 6.0.0. I've attached a minimal example to reproduce it. Note, it doesn't have to load an actual qml file into the QQuickWidget to trigger the bug, however, if the setFormat() call is commented out, the content of any qml file is displayed correctly (but without anti-aliasing).