Sami Fathi, MacRumors:

macOS Monterey, released last week as the latest version of macOS, is bricking older Mac computers, rendering them unusable and unable to even turn on, according to a number of reports from users across social media and online forums.

And:

If this sounds oddly familiar, it may be because last year, with the launch of macOS Big Sur, similar reports surfaced about that update bricking older MacBook Pro models.

No answers here, but plenty of tweets from owners of newly bricked Macs. If you’ve got an older Mac and are considering upgrading to Monterey, definitely read through the post, maybe wait until macOS 12.1 drops.