Regarding USB-C I agree with you entirely and think you entirely missed the point I was trying to make. I am well aware Apple participated in the USB-C connect

Regarding USB-C I agree with you entirely and think you entirely missed the point I was trying to make. I am well aware Apple participated in the USB-C connector specification processes and only introduced the Lightening port when it became clear to it that USB-C would take longer to define than their urgency to ditch the old iPod 30-pin connector would allow, forcing them to ‘defect’. They’re probably rather sour about this deep down (since it forces them to have different “one size fits all” interfaces on different lines of products, which kind of undermines its own point). At any rate, the thought I was trying to express is that I would be very surprised if Apple adopted any kind of ‘standard’ ARM architecture from upon which to begin its new era of ARM-based Macs. They’re not even calling them ARM-based, they’re using the term “Apple Silicon” (which is only a marketing gimmick but it’s pretty indicative). So... they might, during the course of their preliminary analyses and feasibility studies identified a pre-existing ARM system architecture that they are comfortable with, but most likely they’ll go for something unashamedly homegrown such as whatever architecture they developed for the iPhone and iPad and consequentially whatever boot procedure they follow, which as far as I know is undocumented and subject to change (though it is the regular target of reverse-engineering, because of jail-breaking... and that game of cat-and-mouse has probably greatly enhanced code quality and reduced exposed surface area). The end result is that “from the inside” from a very low level (the kinds of hardware levels) that matters when booting an OS and that it subsequently screens userland and the users from, these details matter, and I don’t expect them to be standard, I don’t expect them to be clear, and I expect that unsigned OS images won’t be bootable. That said I read that Apple has had a session at the WWDC 2020 about booting other OSes from external drives on the ARM Developer Transition system, so who knows, I could be wrong.