Howard Oakley:

One document every serious Mac user should read and refer to repeatedly is the Platform Security Guide, which Apple has just revised to give all the gory details of how M1 Macs start up. In the course of doing that, it reveals that these new models have a boot mode which doesn’t appear to be documented anywhere else, but which could prove a Mac-saver: Fallback Recovery OS.

Here’s a link to Apple’s Platform Security user guide.

More from Howard:

If you need your M1 Mac to enter 1 True Recovery (1TR), Recovery Mode, but that fails, there’s a second copy of the software required for 1TR “for resiliency”. To boot into that, instead of just holding the Power button until 1TR starts loading, you should “double-press and hold the power button”, according to the guide.

In practice, I’ve found this requires you to press the Power button twice in rapid succession, and on the second press, instead of releasing the button, hold it pressed until recovery options are reported as loading. This works reliably on an M1 MacBook Pro, but I’ve so far been unable to get it to work at all on my M1 Mac mini, but maybe I’m just not doing it right.

If you are responsible for the maintenance of an M1 Mac, this is worth a read and a bookmark.