I am having difficultly trying to install Loki on my MacBook circa 2007. Firstly following the instructions and using Etcher to burn elementaryos-0.4-stable-amd64.20160921.iso I created a USB stick that booted fine on my mid 2012 MacBook Pro but not on the 2007 MacBook.
I found this blog post https://ubuntuforums.org/showthread.php?t=2266424, and following its instructions of copying bootIA32.efi from Mac Linux USB loader I was able to boot off the USB stick. However when I try installing it always errors with this
grub-install /dev/sda' failed. This is a fatal error
I've tried about half a dozen times and enabled the internet during installation to no avail.