Hello everyone,
to avoid this information wilting in some Discord channel, here’s my repo with Arch Linux ARM-related information:
https://github.com/kleinesfilmroellchen/chrultrabook-arm-stuff
This may be useful to you if you’re trying to build your own Linux images for ARM (even if not specifically Arch). Note that I have not verified that this actually boots, since I currently have other hardware issues. I’ve also uploaded a patched submarine image that boots on juniper-hvpu, and the dumped and decompiled device tree from this board.
I also fixed the vboot-utils package, so you can use this instead of the AUR one.
I have a slightly tweaked u-root image with junk removed and localboot added so you can boot straight away without showing menu.