Well, apart from actually doing some bike fettling this week, including a very short ride, I have mostly been wrangling Apple Macs.
As they are both pretty old, the versions of macOS they will run range from useless (El Capitan) to OK-ish (High Sierra). So Linux is the order of the day.
Late 2009 Core 2 Duo 27" iMac: doddle. Standard USB stick, plug it in, boot it, install it. Job done. Just like any old Windows box. And what a beautifull 1440p screen!
Early 2008 Mac Pro, model 3,1: absolute friggin' nightmare. Would not even see the stick as a bootable device. Surprisingly, there was no knowledge I could find as to why this might be. I tried formatting the stick every which way. Nuffin. Then, just in case, I tried a different stick. For the record, this was USB3 and much larger capacity, neither of which should matter at all. Bingo! There it was in the Mac EFI boot screen, and selecting it produced a GRUB menu. Now we're cooking! Hit enter to run the live image, as usual. Zip. Just sat there with a static cursor in the top left-hand corner. Next, I burnt the ISO file to an external SSD and tried that. Same result. Then, out of sheer desperation, I took the SSD out of its case and plugged it straight into the Mac Pro backplane.
It bloomin' worked. Having figured out how to do it, I switched it all off, installed all the drives I wanted the machine to have, and went for it. Flawless install, and it runs really well. After that, deciding I don't need to see the Mac boot screen, I added an Nvidia GT1030 and connected the monitor to that. Linux did its thing, and I'm now able to use the full power of the GT1030 or switch back to the Mac native Radeon HD2600XT for power saving, or if I need to swap a macOS drive back in. The Nvidia card is invisible and useless to macOS, which has rarely played well with Nvidia kit.
So now I have a very stylish and quite powerful Linux box, twin 2.8GHz Xeon X5462s and 16GB RAM. Not bad for £20.