Endeavouros onto Chromebook
Having tried Manjaro I decided to give Endeavouros a go and the same problem, with a similar fix.
I then booted this on the Chromebook and the install worked until installing bootloader failed.
The solution is to open a terminal and enter
Hint: use tab to complete the numbers after root
Then retype the failed command and add
Hint : If you leave the installer error visible you can copy and paste into the terminal (CTRL+SHIFT+V)
This works without error.
sudo grub-mkconfig -o /boot/grub/grub.cfg
Then run the cleanup script
Reboot and all should be good.