Force Windows to not use laptop's dGPU during boot?

I have a very unusual issue with my Thinkpad T480... it won't boot Windows.

That's not unusual I hear you say but hold your horses there, Tom Jones.

First, a bit of backstory. Please read it as it should explain that the issue I have, is not your average boot problem.

My T480 has two GPUs. The iGPU on the CPU, and an Nvidia MX150 dGPU. If the OS in use supports it, the OS can dynamically switch back and forth between the iGPU and dGPU. When the dGPU is used, it just does the heavy lifting before sending what it has rendered to the iGPU for display.

When I first got my T480, I was able to detect and use the MX150 in both Windows 10 and Linux. I was able to install and interact with the Nvidia driver on Linux. Then came an extended period of time in which I did not boot into Windows (as I had switched to Ubuntu as my daily driver). When I finally had the need to boot Windows again, I found that the boot sequence would get a few seconds into displaying the spinning circle of white dots, the dots would freeze in the same position, and then my T480 would reboot. On rare occasions the boot process would display a message saying that startup repair was running.

Skip ahead and after a whole load of dead ends and testing, I found that my T480 functioned seemingly without issue. I could boot anything I wanted to, as long as it wasn't Windows based... Numerous distros of Linux, various flavours of BSD, various boot / rescue discs.... everything, as long as it wasn't based on Windows. I tried Windows 10, 8, 8.1, 7... I think I may even have tried Vista. I tried Hiren's, I tried the Macrium Reflect boot disc. Nothing would boot on the T480 but all of the ISOs could be booted on my desktop.

I should note at this point that I also tried individual toggling every BIOS setting, and I tried flashing the UEFI to a few different versions but to no avail. I also tried using the physical, Lenovo factory reset button.

I couldn't for the life of me figure out why my T480 hated Windows so much.

Then I had a breakthrough when I found one other user, amidst the seemingly endless see of people with your more typical boot and boot media issues, that had all the same symptoms I had, and on a T480 to boot (if you'll forgive the pun). Specifically, they had a T480 with an MX150 was no longer showing up when being queried it using terminal commands on Linux.

Sure enough, I ran the same commands and my MX150 is nowhere to be found. When I tried installing or interacting with the Nvidia driver on Linux, it would say that no Nvidia GPU was found. The same too was true of various tools related to the dGPU, such as Bumblebee (which allows users to selectively switch between GPUs, disable GPUs, etc.).

So here's my theory...

My MX150 is either physically dead, or it has been disabled somehow. For whatever reason, this doesn't present an issue for FOSS stuff but I think it must be an issue for Windows. My theory is that when Windows boots, it's trying to do something with the dGPU, failing, and then rebooting the system. What I'd like to know is whether it's possible to force Windows 10 (or any Windows version for that matter), to not interact with the dGPU during startup?

 

I wish I could but the MX150 in the T480 is soldered to the motherboard.

 

If you're able to provide any links to threads where a user has a dead MX150 in their otherwise working laptop please, I'd appreciate it.