Laptop display (4k) not working in Big Sur [Lenovo ThinkPad X1 Extreme Gen 1]

Hardware:

• CPU: Intel Core i7 8850H 2.60GHz (Coffee lake 8th Gen)
• GPU: Intel UHD Graphics 630
• RAM: 32 GB 2667 MHz DDR4
• Motherboard/Laptop model: Lenovo ThinkPad X1 Extreme Gen 1
• Audio Codec: Realtek ALC285
• Ethernet Card: N/A
• Wifi/BT Card: BCM943602CS
• What guide/tool followed: dortania's guide
• What part I got an issue with: Laptop display (4k Internal)
• What files/config I am using: Nothing out of the dortania's guide
• Extra Info:

So basically, everything works fine, smooth as hell, actually — except the laptop display. It's a 4k though and it used to work just fine under Catalina (10.15.7).

What I tried, unsuccessfully:

• Every Framebuffer/DevIDs listed under WhateverGreen/FAQ.IntelHD
  • ended up with the following, which let me at least use my external monitor with full iGPU acceleration.
    • AAPL,ig-platform-id: 0900A53E (0x3EA50000)
    • device-id: 9B3E0000 (0x3E9B)
• Patching VRAM
• Patching Bus IDs using the dortania iGPU guide, using alldata method
  • framebuffer-con0-alldata: 00000800 02000000 98000000
• Patching EDID to lower the refresh rate of the display from 60Hz to 48Hz, using the guide here
  • ended up with the following, although using this patched EDID doesn't seem to make any difference
    • AAPL00,override-no-connect: \*\*patched EDID\*\*
• Using -igfxmpc as boot-args to enable max pixel clock override

At this point, I'm not sure what I have missed. I'm using an external monitor to post this rn. I would really appreciate if anyone can guide me in resolving this issue. Or please share the DeviceProperties section if you were able to get your 4k internal display working on Big Sur [Coffee Lake, UHD 630].

Also, please hit me up with any questions you may have regarding my build. I'm happy to answer them.

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https://preview.redd.it/fd8q0xue0j971.png?width=770&format=png&auto=webp&s=e90185913a0a69ff0eabbb7a0e48f331a980767a