“The device you inserted does not contain ChromeOS”

One question? How does it check this? is it via checksum or how?

it looks for the board specific signing key, IIRC.

if you flash a USB with the recovery tool cant you just yoink that signing key and put it on soemthing else?

it’s not a file, it’s a signature applied to the kernel

Yeah ik but maybe in some way you could like write that key to another kernel (not if it’s like a checksum)

ofc, that’s what all the ARM distros do

Yes but then you need to run crossystem dev_boot_signed_only=0 to allow kernels not signed by google