I'm trying to install Elementary OS Luna (based on Ubuntu 12.04 LTS) on my iMac from 2008.
At first I tried the straightforward combination of
dd to a USB drive, which failed to even show up using rEFInd or holding option.
There is a bug report that requests a Mac ISO, but the conclusion is
This is no longer necessary to install elementary/Ubuntu on a Mac
My second attempt was with https://github.com/SevenBits/Mac-Linux-USB-Loader
This makes the USB bootable. But only when holding option. rEFInd doesn't see it.
So I boot the Live USB and open the Ubuntu installer and proceed to partition a swap and ext4 partition. The installer almost finishes, but crashes on installing grub.
I tried several times on sda, sda1(EFI) and sda6(ext4), all fail.
Then I tried manually installing with
sudo grub-install --root-directory /media/the-mount-point /dev/sda6
This completed after I marked sda6 as a bios partition in gparted.
Now when I boot it shows up in both rEFInd and when holding option, but when selected displays just a cursor.
I'm out of ideas. I don't care if I do legacy or EFI booting, as long as I do any booting at all...