Yes, that's unfortunate - the lack of drivers means that Linux devs will once again have to reverse someone's proprietary software to develop their own drivers. It's not a fun state of affairs. Unfortunately, Apple is not likely to start fully supporting Linux on Mac hardware by providing drivers and documentation. But the point here is that they haven't done anything technically to prevent you from running Linux.

> Unacceptable. The user must disable Secure Boot to run Linux, which means the system becomes vulnerable to bootkit attacks.

I see this said a lot, and I find it baffling because so many Linux users demanded no secure boot at all - which is exactly the thing being called unacceptable now. (It's not just you; The Register, for instance, complained about how "malware or malicious users that gets onto your Mac can potentially alter the operating system to hide spyware right from startup" when secure boot is off, in an article otherwise complaining about how Apple must hate Linux users because secure boot is now on.) There is no increased risk of bootkit attacks to Linux users as a result of this change. There is simply a reduced risk to macOS users.

I do agree that a model (as MS implemented) where you can enroll your own keys would be better - but that would be a new feature. In the meantime, if every Macintosh from the 128K until today was acceptable, what changed?

The white paper addresses this - the UEFI CA is not included in the secure enclave's trust store. This is intentional - the UEFI CA is used to sign bootloaders that don't perform chain-of-trust validation, meaning that if the secure enclave trusted the UEFI CA by default, then secure boot could be pretty trivially bypassed.

Sure, they could make things more secure by allowing you to add your own keys. You could go ahead and add the public key for your secure bootloader that does chain-of-trust validation, but the "typical scenario" would be a user adding a generic UEFI CA that leaves them open to a modified or malicious OS.

> And, the typical scenario will be a user who leaves it disabled, making both macOS and Linux and possibly Windows (if also installed) more vulnerable to bootkit attacks.

No way. The typical user will leave it enabled because they will only use macOS.