I'm seeking help and would like to have a discussion about booting Linux on Apple hardware using an EFI boot loader. Probably not going to be a popular suggestion considering one of your sponsors is System76 but I thought I'd give it a try regardless.
I came across a great tool called "Mac Linux USB Loader" which is still under heavy development. "This is the Mac Linux USB Loader, a tool allowing you to take an ISO of a Linux distribution and make it boot using EFI."
I spoke to "SevenBits" the developer and there's an unresolved problem he hasn't been able to fix, which affects myself and others who use older Macbook Pro hardware (late 2008 4,1 and others).
"I actually have an early 2008 MacBook Pro which also fails to boot Linux. I test the bootable drives my tool creates on a newer, separate machine. I believe with 90% certainty that the reason for this problem is the lack of Linux kernel mode setting (KMS) support in Apple's EFI firmware, which is required for nVidia video drivers to function properly. Disabling KMS in the boot options of most distros actually causes the splash screen to show up, but then X (the graphical windowing system used to provide a desktop) can't start because KMS is disabled, and so you are dropped into the terminal with a bash shell. If you like command line Ubuntu, this is fine, you can just connect to the web via Ethernet (and even install WiFi drivers) and go, but for 90% of us, this is an inadequate solution."
Have you, or anyone you know had success finding a solution to this problem?