It's like the black screen forces the GPU into some weird state it can't recover from but only in Windows. Bios etc' is fine..
If you were to uninstall GPU drivers with DDU, would your GPU show image on Windows?
Now, all GPUs work with Windows display drivers, hence why you can see BIOS and Windows, once you 1st install the GPU. But to use GPU fully, you need dedicated drivers.
It's like when you buy mechanical KB or gamer mouse, that has control software (e.g Corsair iCUE with Corsair peripherals). Does the KB/mouse still work without dedicated software? Yes. But to use the said peripherals at their full extent, you need the dedicated software/drivers.
What could be issue with your GPU, is that it's on-board driver chip has a fault, hence why GPU works on BIOS and on boot up, but once drivers are loaded, it won't work anymore. Due to that, i also think your GPU works when you uninstall drivers with DDU and use Windows built-in display drivers.
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This is where i end my help to you, since you're essentially hijacking someone else's topic. If you want more help, make your own topic.