
Honestly this is as much for my own memory as anything else, but if you're interested: a couple of months ago, housemate Paul brought his mom's old 2006 Mac Mini back with him from a visit. He'd asked if I wanted it, and I said "sure, I can upgrade that, probably get Linux on it, maybe use it for something."
"Something" turned out to be a PLEX media server. It's really good at that. But its 32-bit processor and 512M of RAM was obviously not going ot be enough.
Upgrading the Mid-2006 Mac Mini to install and run 64-bit Linux
First and foremost: HAVE OS X STILL INSTALLED. You won't need to keep it, but you'll need it at first.
Install a socket-compatible 64-bit processor, like the Core 2 Duo 2Ghz. (2.19 is available also but costs a lot more.)
Then and only then boot to OS X and use the firmware upgrade hack floating around online in retro/old hardware circles. This runs under OS X, which is why you need that install. It makes the Mac Mini think it's a Mid-2007, not 2006. Do this even if your 2006 came with a 64-bit processor (a very few did), because this upgrade makes the 2006 Mini capable of booting with more than 2GB of RAM.
Then upgrade to 4GB RAM and install new HD. This results in a Mac Mini Mid-2007 with 32-bit EFI and 64-bit processor. For some reason Thanks to issues in Intel's Northbridge design, only 3G will be usable - the rest is mapped to various I/O functions and video display, whether you want it to be or not.
Ubuntu 14.04.6 is the LAST version of Ubuntu to have an "amd64-mac" build, which specifically supported install to 64-bit Apple systems with 32-bit EFIs. In theory, you should be able to do this from a USB stick, but in reality, you cannot. It must be burned to optical disc. Then it will install fairly normally.
Once installed, it will note there is a new LTS, and ask if you want to upgrade. Do so immediately. This version will then ask the same question. Do so immediately. Repeat until running current 64-bit Ubuntu Linux.
Upgrading the Mid-2006 Mac Mini's Hard Drive
Once the Mini was set up and being a surprisingly good PLEX server, we realised we'd need a larger hard drive.
You can clone an existing drive to a larger drive. Unlike PC architecture systems, you cannot clone to a slightly smaller drive and rely on the last partition being swap that you modify, or delete and re-create, because of the way Macintosh systems set up their partition tables. It WILL corrupt and it WILL fail to boot. (Yes, this sounds counter to the point, but there were reasons to try this at one point.)
NO MATTER WHAT, DO NOT LET GPARTED "fix" THE LOCATION OF THE PARTITION TABLE. ALSO DO NOT USE GPARTED TO INCREASE THE SIZE OF A PARTITION. THE DRIVE WILL BE CORRUPTED AND YOU WILL HAVE TO START OVER.
However, you can create a new partition with gparted so that you can use the extra space.
Installing Linux to a Mid-2007 Macbook
This hardware is very similar to the hacked Mid-2006 Mac Mini, as well as being very similar to an actual Mid-2007 Mac Mini.
The optical drive in this Macbook was dead. It is possible install from optical media would've worked fine, and similarly to the Mac Mini. Update: Having received and installed a replacement optical drive, I can confirm the install DVD-R boots normally and 14.04.6 can be installed in the same way as the Mac Mini.
Many attempts to install via USB stick failed - see list of useful sites below - because while I could get the USB stick to show up as a boot device, the EFI bootloader would work, the RAM drive would set up properly, but then the attempt to boot the kernel would fail every time no matter what solution (or kernel bitsize) was used.
WHAT WORKED: Cloning the successful Mac Mini install (above) to a new, larger drive. Installed the larger drive back in the Mac Mini (because media server), and the original in the Macbook. THIS WORKED FINE.
Resources specifically to 32-bit EFI/64-bit processor systems, found during the Macbook project:
Linux DVD images (and how-to) for 32-bit EFI Macs (late 2006 models)
https://mattgadient.com/linux-dvd-images-and-how-to-for-32-bit-efi-macs-late-2006-models/
These are 64-bit images other than 14.04.6 Ubuntu Linux, the last version released by Ubuntu to specifically support install on these models. If you don't trust his images, he tells you how he made them.
xUbuntu single-boot on mid 2007 Macbook, USB/FW install, no REfit/Refind
https://ubuntuforums.org/showthread.php?t=2266424
This is how to install 32-bit images via USB stick. It DID NOT WORK on the Macbook and should have. It did get the Macbook to the point of seeing the boot point, and it would try to boot but would then hang when specifically trying to boot the Linux kernel.
Live CD on an USB Stick (32-bit EFI, 64-bit Linux)
https://mesom.de/efi32boot/index.html
This DID NOT WORK for the Macbook, but should have. It did get the Macbook to the point of seeing the boot point, and it would try to boot, but hang, probably when trying to boot the Linux kernel. The Mac Mini (being actually 2006 even if it thinks it's 2007) doesn't support booting off USB.
MacBook Pro Mid 2007 Not Showing Linux USB In Boot Menu
https://apple.stackexchange.com/questions/248387/macbook-pro-mid-2007-not-showing-linux-usb-in-boot-menu
Mid-2007 Macbook Pro have 64-bit EFI, and this should work for those systems.