Something else you can try is creating the live USB using dd, rather than one
of the live USB creator tools. There are instructions for how to do it on
this page:
https://askubuntu.com/questions/372607/how-to-create-a-bootable-ubuntu-usb-flash-drive-from-terminal
(note that it regrettably doesn't use free Javascript)
For some reason that sometimes seems to work where the GUI tools don't. I
have no idea why. I remember having to mess about a bit when I did mine.
Literally all you need is to get some form of GNU/Linux working on it, so you
can flash the annoying Apple firmware.
