Status

Can load GRUB2 from a fat partition on the UFS.(/firmware is tested,you can also format the useless /cust for it)
Windows boots with original 8998 ACPI tables, but you'll need to add UseBootProcessorOnly to your BCD boot options,
as the multi core startup haven't been taken care for now.

Working

Continuous Display
UFS Storage
Vibrator
...

Not Working

Clocks
...

Building

Tested on Ubuntu 18.04.

First, clone EDK2.

cd ..
git clone https://github.com/tianocore/edk2.git --recursive
git clone https://github.com/tianocore/edk2-platforms.git

You should have all three directories side by side.

Next, install dependencies:

18.04:

sudo apt install build-essential uuid-dev iasl git nasm python python-pip python3-distutils gcc-aarch64-linux-gnu abootimg p7zip bsdiff
sudo pip install uefi_firmware

Also see EDK2 website

Then, extract the XBL binary from your device (the powerful dd will serve you), name it xbl.elf and put it to current directory. Execute ./extract-xbl.sh to get the proprietary blobs extracted:

./extract-xbl.sh

Finally, ./build.sh.

Then fastboot boot uefi.img.

Credits

This is based on zhuowei's edk2-pixel3.
SimpleFbDxe screen driver is from imbushuo's Lumia950XLPkg.
Special thanks to @lemon1ice, @gus33000 and @imbushuo for guidance.

Notice

I have never posted any photos/videos about this project on public media. All videos, photo posts, news etc, are NOT posted by me. 我从未在网络上公开发布过任何与此项目有关的任何图片或视频，任何网络上相关视频(Bilibili/youtube)均不是我发布的，发布这些内容的账号均与我本人无关。 edk2-sagit源码仅在此repo发布。 以下视频并非原创

视频：https://www.bilibili.com/video/av497635981（https://www.bilibili.com/video/BV1xK411L74d）个人主页：https://space.bilibili.com/341690282