Can I use terminal to install Grub on an external backup HDD via USB, or do I have to do it in Single User?
Just create the EFI partition (FAT32)
Follow instructions in section 3 from brainshutdown's github:
I did a little digging and I don't think it's possible with MacbookPro10,1s yet:
Notice the "power down" dGPU outb numbers don't work (just crashes my machine)
Which is consistent with this post:
Do you think there's away around it brainshutdown?