State here in GNU Grub about Arm
there no legacy , or bios mode on theses motherboards
in case for Apple , if there is always any /boot/efi means a Secureboot or shim used
if clover is being rewrited for more openboot , there is a reason
as all hardware Apple will be blocked in time on version Ios ( 6 to 8 years ) ,
only linux ( or you want to fight to get a BSD ) can be up to date.