GRUB scripts generated from common GNU/Linux distros are generated by a program inside the distro: it detects partitions and operating systems then writes the grub.cfg file inside /boot directory that contains the necessary menu items to boot whatever is detected inside.
The script generated by mklibrebootgrub do not work that way: you have to specify, precisely, what do you expect to find together with more options. Do not expect the same autodetection capabilities like the ones of Super GRUB Disk.
You will be prompted to enable or disable features according to your needs but keep in mind that you cannot use whatever is not being supported with the Libreboot’s GRUB payload or what is not supported by the computer itself.
To make an example you cannot enable NVME support on a GRUB payload that doesn’t have NVME support compiled or the machine itself doesn’t have any.
To make it short, you need to know what you want (or not) to boot and on what machine it will run.
Clone the repo
Configure the script
On the command line type “make nconfig”. There are other three make options (config, mconfig and qconfig) they basically do the same but with different user interfaces. Once you are done with configuring save the configuration.
“Compile”
Just type on the command line “make” and you will see a grub.cfg file appear. This file will be used to replace the stock “default” Libreboot’s GRUB one. Now you need to build your Libreboot image again and you are done. Eventually, use cbfstool to replace grub.cfg file in it.