For all who are still running Yosemite (OS 10.10) on their old mac, NG on UNetbootin and Etcher.
Luckly, I did get Linux Mint working on my Acer Chromebook 14, downloaded Etcher, made it executable, then clicked on it, follow simple instructions, and made a bootable USB.
Then I booted that USB on my Mac Pro tower!!! I didn’t think I can make a bootable USB on a Chromebook for a Mac…
BTW, when I booted from the USB to test drive Mint. Printers, graphic tablet, external sound all work!!! Problem with internal sound and keyboard though…