I can’t see your photos, but I am currently dual-booting between Ubuntu 21.10 (64 bit) and MacOSX 10.7 on a MacBook 2,1 without troubles. Although you can usually hold down the option key during initial boot-up to bring up the Mac’s BIOS boot selector, and then select either the MacOSX 10.7 partition or the GRUB/linux partition, to make things simpler, most walkthroughs recommend installing rEFInd <https://www.rodsbooks.com/refind/index.html> which gives you a nice graphical menu of your available bootable systems to choose from. There are various walkthrus available, and all of them seem to recommend rEFInd as well — not doubt I followed one of these several years ago HTH, K |