And then there is the OS which is getting more and more locked down so that you can not run unsigned software without increasingly difficult workarounds.
On one hand, alternative OS support on macbooks has gotten worse and worse over the last few years but it is sad to see the final nail in the coffin.
Locked bootloader only booting stuff signed by Apple.
So these CPUs can only be used to run MacOS, no Linux or other alternate open platforms.
ARM doesn't have a generic platform like PC but I'm sure someone will figure out how the device tree works if they haven't already.
Gotta take their 30% cut of everyone's revenue.
The BSA/SBS is relatively new as far as I'm aware. The server version was released in 2014, the same year as the iPhone 6 which was already using Apple SOCs.
I don't know when the client version was released but fairly recently AFAIK. I don't know of any systems shipping based on it.
Most ARM systems are using device trees and their own custom slate of devices.
So I should amend my comment I suppose: no one is using any kind of "Standard ARM PC" definition in any quantity, and I'm not sure we should bring over UEFI or ACPI when device trees have been working well so far.
Nevertheless as I noted I'm sure enterprising hackers will figure out how to do it. If you downgrade security the SEP will sign whatever "kernel blob" you like and the system will load and jump to it at boot. Technically that isn't even required - a kext could pause all CPUs, set the correct registers, and jump to a completely different OS if you were really determined.