This worked for me:
- VirtualBox > edit VM settings to enable EFI
- use a USB 2.0 memory stick and plug into a USB2 hub, plug that into MacBook Pro USB C port
- add that USB stick to the VM using EHCI (USB 2)
- Boot VM, it will fall back to the virtualbox EFI shell.
- Let startup script auto run. Run this:
- fs1: (or wherever your usb disk landed)
- cd EFI-\boot
- bootx64.efi
- Lime Technology EFI boot menu should start here and let you select Unraid