Unwanted transparent menus with windowsvista style

With Qt 6.8:

Before with Qt 6.6.3:

In 6.8.0 with windows11 style menus are fine:

(but most other stuff is simply ugly; but at least now the spinboxes are usable again)
With 'Windows' style:

menus are fine too, same with 'Fusion'-style:

Only style broken on Windows seems to be 'windowsvista'.