For older systems that lack UEFI support, the mbr-gpt hybrid approach allows booting from GPT disks by using a specially crafted MBR that understands the GPT structure. The resulting MBR code is extremely compact (must be ≤440 bytes) and is written in pure assembly language.
This produces a file like mbr_1.2.1.tar.xz , which you can convert or extract. mbr support.tar.gz download
Typical files you might see: