Hello
@mango1122 ! thanks for posting this comprehensive process and files. I think there are a couple of points of confusion or flaws in the guide currently.
As you mention steps 1-3 are not strictly necessary. most importantly step 1 is very unnecessary as the firmware will be completely overwritten as nvm20 when it is programmed by SPI. As many people have struggled to do an official firmware update on this board i suggest removing this step. it is just going to confuse people. I do agree it is still a good idea to have people backup their existing firmware (steps 2/3) before starting the process so they have a known good firmware to fall back on if they run into unexpected problems.
I am not 100% certain about this but i do think that force power needs to be enabled before people can achieve a thunderbolt tree. So i think this is a little out of order in your process instructions. Possibly that should be the actual first step so that its ready to go as soon as firmware is flashed. And then as you state people can finally verify thunderbolt tree and go through the process linked to create a valid TDROM SSDT.
Lastly, did you find it very difficult to read/write with the SPI programmer to the chip on this board? Reason i ask is most reports indicate that it can be very difficult to read and write to motherboard onboard chips (vs relative ease with add-on cards). If you did not struggle with this at all, that is great news and may indicate this board is much easier than most. If you did struggle with it please see the updated flashing instructions Casey posted today as they may also apply to this (and most) motherboards to make flashing much, much more easy/reliable.
Thanks,
g\