No support for VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR?

I’m trying to get alpha compositing to work, in other words, to get a window alpha-blended with the rest of the desktop.
It’s possible with intel integrated graphics.
With intel integrated graphics it even works with VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR (though that might be a problem on their part, works for me, I’m not complaining).
I know nothing about drivers and graphics cards, but this sounds like something that would be simple to do, since it’s just “do nothing to it, and let the OS handle it”.
I would just like to be able to do transparency without having to render to bitmaps or use whatever other cumbersome, slow methods.
It’s possible with directx. Is this a mistake on your part or am I doing something wrong?