First, download the Enterprise bootloader from https://github.com/SevenBits/Enterprise
Format your USB stick as FAT32 with MBR - you can do this in Disk Utility on the Mac.
Create a folder called "efi" in the root of the stick, and then create a subfolder called "boot"
From the Enterprise bootloader, copy the two files boot.efi and bootX64.efi into the /efi/boot/ directory on the stick.
Copy the PIXEL-x86 ISO file into the /efi/boot/ directory, and rename it "boot.iso"
Finally, create a file called "enterprise.cfg" in the /efi/boot/ directory, with the following contents:
Code: Select all
autoboot 0 entry Debian family Debian initrd /live/initrd1.img kernel /live/vmlinuz1 findiso=/efi/boot/boot.iso boot=live config live-config quiet splash
Reboot your Mac with the stick inserted, holding down Alt. When the boot menu appears, there should be an option "EFI Boot" - select that and see what happens. With any luck, Debian with PIXEL will appear.
This mechanism does not enable persistence; to do that, a more complicated procedure will be required to partition the stick, which I haven't tested yet - bear with me...