Google Pixelbook i7 Installs but can't read boot disk.

Hello! I am trying to dual-boot Gallium OS using chrx on my i7 Pixelbook (Kaby Lake).

I followed the instructions on the chrx website.
Note, I did NOT update my firmware as was recommended, but not required.
Despite this, everything seemed to go smoothly with the install. The drive seems to have partitioned correctly, and I can mount it from the ChromeOS shell and see that there is indeed a linux file root on /dev/nvme0n1p7. My bootscreen responds to a Ctrl-L and launches SeaBIOS, which leads me to believe the problem was not that I didn't update the firmware? I can still access ChromeOS with Ctrl-D.
However, when I try to boot to GalliumOS using Ctrl-L, I get the following screen:

I tried to resolve the issue using the instructions here: mounting the partition from ChromeOS shell and running dpkg-reconfigure grub-pc to reinstall GRUB. This seemed to work without giving any errors, but it does not resolve the issue.

Do I have to undo the hardware RW protection and update the firmware? Or do these symptoms suggest it is not a firmware issue? (As it gets to the SeaBIOS screen on Ctrl-L without issue) Other people seem to have gotten this working on the Pixelbook, does anyone have any ideas? Thank you!!

reynhout / chrx

Google Pixelbook i7 Installs but can't read boot disk. #74