Cannot boot without disabling iGPU acceleration

Hello, I seem to be having an issue with GPU acceleration. Whenever I use the -igfxvesa boot argument the computer boots up fine but there's no graphics acceleration and the VRAM on the "About My Mac" pane reads 7 MB. This is intended behaviour AFAIK.

However, if I do not use this boot argument then my computer:
Reboots itself after verbose if I use any framebuffer with nonzero connectors other than 0x3E9B0007.
Smears the screen and/or reboots itself if I use a headless framebuffer (zero connectors)
Sits with a black screen if I use framebuffer 0x3E9B0007.

I've tried:
Every framebuffer 3-4 times
creating and using a device-id field
BusID patching on each combination of 6 busIDs and 3 indexes with connector type 0x00000002 (meant for internal displays like mine, AFAIK)
-igfxblr igfxonln=1 igfxfw=2 -igfxvesa agdpmod=pikera -igfxmlr boot arguments in varying combinations
Macmini8,1 MacBookPro16,1 iMac20,1 SMBIOSes
CPUID spoofing (I was told that the CPU extended model 0xA5 was not compatible with the Big Sur kernel, so I spoofed it to 0x8E with Cpuid1Data E2060800 00000000 00000000 00000000 and Cpuid1Mask F0000F00 00000000 00000000 00000000
(That said, I didn't try every permutation of these variables, only enough to make the above statements true)

Here is a google drive folder with the resources I've gathered surrounding this issue: https://drive.google.com/drive/u/0/folders/1-k29SMOAdNiBwyDAHl3-RjI8jFt6bRkF
EFI 1 is the EFI folder I had when I started tackling this issue.
EFI 2 is the EFI folder I have now with the issue still unresolved, even though I've made a bunch of other fixes in the meantime.
4.jpg was a screenshot I managed to take by blindly logging in and opening the "About my Mac" pane on a boot with framebuffer 0x3E9B0007 and no -igfxvesa boot argument.
5.jpg and 6.jpg I took on a boot with the -igfxvesa boot argument. They are clearly missing some fields that contain necessary information to properly follow the Dortania BusID patching guide for framebuffers, so I'm at a loss in that regard.
withvesa.jpeg and novesa.jpeg are photos of the verbose log around where I assume the iGPU would initialize when I included or didn't include the -igfxvesa argument, respectively.

Computer specs:
Laptop: Lenovo X1 Extreme Gen 3 (20TK001JUS)
CPU: Intel Core i9-10885h (Comet Lake)
Mobo: WM490 chipset
iGPU: Intel UHD 630 Graphics (Device ID 9BC4)
dGPU: Nvidia GeForce GTX 1650 Ti with Max-Q design (Turing architecture)
Storage: Western Digital PC SN730 SDBQNTY-1T00-1001 (1 TB SDD)
Memory: 32 GB DDR4-2933 MHz
Wireless: Intel Wi-Fi 6 AX201

Bootloader: OpenCore 0.6.8
macOS version: Big Sur 11.3 and 11.4 beta (I've tried both)
Guides I've tried following: Dortania and the "General Framebuffer Patching Guide using Hackintool" on the forbidden site, along with the the WEG documentation on Intel GPU framebuffers

Product specification reference:
https://psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_X1_Extreme_Gen_3/ThinkPad_X1_Extreme_Gen_3_Spec.pdf

Any information on this topic is appreciated. I've been banging my head against the wall because of this for 6 days now and I don't think trial-and-error with config.plist settings is the best way to go about this anymore. If I've been forgetting the Hackintosh equivalent of "did you turn it off and then back on again" then I wouldn't be surprised at this point.