I had a old 2006 mac mini lying around. it had a dead cd drive and a flashing folder when I turned it on, so I decided to put it to good use by trying different operating systems on it, I tried lubuntu, manjaro, kubuntu and many other distributions but none of them booted up. So then I find recalbox and try it out and guess what, it worked. But In order to get recalbox working I had to do one more step because it was not as simple as flasing the image onto a usb and starting it up.
this is what I personally had to do:
1.format the hard drive completely with linux (any os should work)
2.flash recalbox into a usb using etcher
3. boot up the mac with the usb
at first recalbox was kinda glitchy and it froze, but it was just a matter of starting it up a couple of times and everything worked just fine. Recalbox on this mac works fine and supports all kinds of usb controllers even arcade sticks.
Hope this helps someone out there