Installing ChromeOS on an MBR device requires a few extra steps compared to a standard UEFI install:

The MBR support tarball often includes a script to re-chain GRUB.

hardware. This file is required because standard ChromeOS and the default Brunch installation primarily target UEFI systems. Where to Download The file is historically found in the Brunch GitHub repository . However, direct availability varies by release version: Direct GitHub File : It was previously hosted in the broimluna/brunchcros sebanc/brunch file lists. Release Assets : Check the Brunch Releases Page