macOS 12 Monterey has made some older Apple iMac, MacBook Air and MacBook Pro machines unusable
Last week, Apple released macOS 12 Monterey, one of several OSes that it updated in October. While the new version of macOS brings several new features to Mac hardware, it has not been smooth sailing for some devices. Incidentally, Apple ties some of Monterey's features to its M1, M1 Pro and M1 Max-based devices.
As was the case with macOS 11 Big Sur, macOS 12 Monterey is causing older devices to crash or brick. Based on reports across Apple's Support Community, Reddit and Twitter, iMacs, MacBook Airs and MacBook Pros have been rendered unusable upon installing the new OS. The issue does not appear to be tied to a particular era of Mac hardware, either. Reputedly, the issue is affecting devices released in 2015 through to last year's models. Only Apple Silicon hardware is unaffected, for reference.
An Apple support document provides a possible solution to the problem, but it is an involved one. In short, Apple proposes resetting the firmware on your device's security chip. However, you must have another Mac to hand running macOS 10.15.6 or later and with Apple Configurator 2 installed. Please note that Apple's solution only works on those that have a T2 Security Chip. Hence, it would not work on devices released in 2015 or 2016.
For now, we would recommend waiting for macOS 12.1 to arrive before upgrading to Monterey, unless you have an Apple Silicon-based Mac. It is unclear when Apple will release macOS 12.1 Monterey, but a public beta is already available.