Macs are problematic with efibootmgr, that could be why your installation failed. I am assuming you did try installing and installation went fine until bootloader installation, follow this guide with 2 details:
- You have UEFI system, don't do the "If the system is installed in Legacy BIOS/MBR
Find your device that holds MBR and install grub" part - Add the
--no-nvram --removableparameters togrub-installcommand