This looks interesting: a boot disk that does a few things. But I’m not sure what this fully does. Little documentation, most of the binaries are provided without source and come pre-zipped. (Be careful with binary-only releases, they might contain malware…) Windows-centric. But it includes multiple bootloaders, dozens of scripts and executables…
The source code (Github site) appears to be new, but there are 2 blog posts >1year old on the topic:
https://github.com/niemtin007/Multiboot-Toolkit
https://niemtin007.blogspot.com/2018/01/how-to-build-multiboot-toolkit-2.html
https://translate.google.com/translate?u=https://niemtin007.blogspot.com/2018/01/how-to-build-multiboot-toolkit-2.html
https://niemtin007.blogspot.com/2017/08/how-to-build-multiboot-toolkit.html
https://translate.google.com/translate?u=https://niemtin007.blogspot.com/2017/08/how-to-build-multiboot-toolkit.html
Firmware Security 