If I set CPU to 68000 in WinUAE CPU settings and boot it will say P96 needs 020 or better, then ignore the P96 and boots "normally" into WB.
So its some kind of conflict with P96, that much seems obvious. (some kind of clash with Display ID?)
As I said before, the real A600 boots fine and displays a picture over HDMI just fine. This is only a WinUAE issue, so some recommendations for settings would be appreciated. ;-)