Primary message is just a big 'Thank you!' Thanks for the inspiration.
I was searching for some replacement hardware as my G5 iMac seemed to be toast. I stumbled across a 24" iMac listed for cheap on Kijiji. The individual had no idea, but it was running Leopard so we speculated it was a match. That was wrong, but it was in perfect condition with 4GB of ram. This old iMac was a full PC with a nice display that can run a firewire recording interface. So I took to cleaning it up, installed Lion and some additional software and it worked like a champ, but no modern browser. Looking on the web this post was top of the list. Anyhow, I was able to use a modified ISO, burn a DVD and install Linux, but only dedicated Linux seemed to work. There were issues getting the second OS to start. Originally I installed Deepin 20.4 from Jan 2022, but it was not leaving my old OSX software to run and I really wanted this to be dual boot. (There was also a mystery about making a bootable USB stick so I didn't have to keep burning DVDs to work from.)
My process in short looks like this. I got varying results depending on the OS, but perhaps I still need to mod the ISO. This made anything I tested boot for install, but the installed OS on the HDD had issues, and I think it's the nVidia card or something in the 64 bit efi files. Anyhow I now have Linux Mint 20.3 running like a champ in dual boot now. The machine is able to run Netflix, and the latest Citrix workspace. So it becomes a great little place to work from home too.
Okay, steps:
1. Download the distribution of interest (amd64)
2.
Patch the ISO (May not be required as it boots without, but I later had video issues.)
3. Format USB as Fat 32. (I did this with Disk Utility as Windows 10 seems to hate doing this for anything over 32GB)
4. Use
UNetbootin to copy the ISO image to the USB stick (I did this in Windows)
5. Copy
bootia32.efi from this jfwells link to the /EFI/BOOT folder on the USB stick (or follow the instructions to create)
6. Boot the Mac holding down the option key. Select the USB EFI and install. (I'm leaving out making free space, etc. I specified swap disk, a /, and a /home using some free space.)
You can use this to install a Live CD to a stick. I suppose if partitioned, a second USB stick could get used for a full install, but that would be slow on USB 2.0.
I have not tested all bits of HW. I don't think there is a way to get proper nVidia support for the newer OS kernel. The nouveau drivers seem adequate, but I can still wish there was something a little better. Things are doing what I want, so I don't think I need to mess around with this anymore.