I’ve been wanting to try this for years, but just got the chance! My daughter gave me her old 2009 plastic MacBook when she bought a new Pro recently, in return for my having provided her support over the years - she knew I’d been wanting to try putting Linux on one. I upgraded the machine a couple of years ago to 6GB RAM and a 128GB SSD. It’s just new enough to run El Capitan, which it actually does acceptably. So I had high hopes for UbuntuMATE!
There are a lot of tutorials out there for doing this, so it didn’t take any genius on my part. Here’s a good one, but there are lots of others:
I used the rEFIind Boot Manager, here: http://www.rodsbooks.com/refind/index.html
The process wasn’t hard, though I did bollix up the disk partitioning part somehow and hosed the original Mac installation (which didn’t break my heart as it was one I’d just done). But if you had a lot of years of stuff stored on yours, it might feel different! In my case, I just started over and got it right. One thing that apparently can happen, and did happen to me, was that in updating the new Mac partition it overwrote the rEFInd boot, so the machine would only boot into El Capitan. But re-installing rEFInd did the trick and it’s worked flawlessly since.
I said that this little box, upgraded with the SSD & additional memory, runs El Capitan well - almost as zippy as Snow Leopard, which it had before - which I guess is some sort of compliment to the job Apple has done with their OS X upgrades.
But one of the charms of dual-booting is being able to see, side-by-side on the same hardware, how well Linux runs vs. whatever legacy OS the machine came with. UbuntuMATE 16.04 runs really well on this machine, palpably better than OS X! It really shows the great effort and success the UbuntuMATE developers have achieved. I’m very, very happy with it!
So no questions here, just wanted to let everyone know how it went and that it would be well worth doing if you wanted to re-energize an old Apple box. Well worth doing, fun in the process, and a great result - go for it!