The same thing happend to me, that is, my 2020 MacBook Pro died last night during the restart while updating with macOS Monterey. I took it to an Apple authorized reseller and they charged me $67.80 ($60.00+HST) for diagnostics...The MacBook is out of warranty, but I am wondering why should I be charged for Apple OS update - related issue that occured last night? Never mind the warranty expiration, and never mind fixing the software problem is "free", I am still out of CAD 67.80. Not really a significant amount of money, but still, c'mon Apple, I cannot use my device, I am wasting my time and I need to pay for it?!