Libreboot supports these machines, which removes the ChromeOS splash screen and the linux kernel size and signing restrictions, otherwise you'll hit problems trying to install the current version of ArchLinuxARM.
There are several guides here: https://libreboot.org/docs//install/chromebooks.html
I used external flashing https://libreboot.org/docs//install/spi.html to replace the firmware because I couldn't get it to write through software. If I recall correctly the write protect is much harder to reach than the chip.
After doing the external flashing once, it is easy to update the ROM with the Chrome fork of flashrom.
Also huge shout out to Alyssa for the panfrost gpu drivers. There was a time when I was following that development very closely and it made a night/day difference to the linux experience.