Having only really studied T2 Macs from afar, I'm now in possession of quite a few 2020 Intel MacBook Airs as well as an M1 MacBook Air.
I was always under the impression that the Secure Boot "Full Security" setting being enabled meant that a given T2 (or M1) Mac would only be able to install the latest macOS release and only be able to boot either what is currently installed (if not the latest) or the latest OS.
I have found that on one of the 2020 Intel Airs, I'm able to use either Internet Recovery Mode (the one that loads the earliest available OS that Mac and the latest available OS for that Mac) and be able to cleanly install either Catalina or Big Sur, respectively. I always figured that Big Sur, being the latest, would be what I could install with "Full Security" turned on and that anything earlier be damned. Is that not the case?
I know the definition of which OS can load is "Operating Systems currently signed by Apple" and that, at least today, on iOS and iPadOS, that's always the latest OS release. I guess I've never seen word of which macOS versions that applies to.
Would Apple be signing the latest Big Sur release, the last Catalina release (10.15.7), and the last Mojave release (10.14.6) since those are what is currently supported (at least on Intel Macs that could run that far back)? Or will Apple always sign the most recent version of any macOS release that can be booted via Internet Recovery (meaning the current OS and, depending on the vintage of T2 Mac in question, as far back as the last version of High Sierra)? Or is it really more a matter of Apple not supporting the ability to boot and install, for example 10.15.6 or 11.4 or 10.14.3, or 10.13.5 given that, for those respective OSes, there's a newer version that Apple is serving up when people go to fetch those particular OS installs?
Apple's documentation on this is EXTREMELY vague.
I was always under the impression that the Secure Boot "Full Security" setting being enabled meant that a given T2 (or M1) Mac would only be able to install the latest macOS release and only be able to boot either what is currently installed (if not the latest) or the latest OS.
I have found that on one of the 2020 Intel Airs, I'm able to use either Internet Recovery Mode (the one that loads the earliest available OS that Mac and the latest available OS for that Mac) and be able to cleanly install either Catalina or Big Sur, respectively. I always figured that Big Sur, being the latest, would be what I could install with "Full Security" turned on and that anything earlier be damned. Is that not the case?
I know the definition of which OS can load is "Operating Systems currently signed by Apple" and that, at least today, on iOS and iPadOS, that's always the latest OS release. I guess I've never seen word of which macOS versions that applies to.
Would Apple be signing the latest Big Sur release, the last Catalina release (10.15.7), and the last Mojave release (10.14.6) since those are what is currently supported (at least on Intel Macs that could run that far back)? Or will Apple always sign the most recent version of any macOS release that can be booted via Internet Recovery (meaning the current OS and, depending on the vintage of T2 Mac in question, as far back as the last version of High Sierra)? Or is it really more a matter of Apple not supporting the ability to boot and install, for example 10.15.6 or 11.4 or 10.14.3, or 10.13.5 given that, for those respective OSes, there's a newer version that Apple is serving up when people go to fetch those particular OS installs?
Apple's documentation on this is EXTREMELY vague.