[magicalhippo]

> it contains enough functionality [...] that it could already be considered an OS itself.

That's what ZFSBootMenu[1] is, an OS to start the OS. And as sibling points out, if you're using EFI you got an OS booting your OS booting your OS...

[1]: https://www.zfsbootmenu.org/

[E39M5S62]

I originally wrote ZFSBootMenu as a reaction to how awful Grub is. I was hacking on the Grub scripts and hitting all sorts of limitations that were just awful to work around (or not possible at all). I used Grub to chain load early versions of ZBM before I had the whole UEFI application build process worked out.