Same issue with an upgrade for an iPad 6th generation - after a system update, iPad becomes visually unresponsive and won't even force reboot, iPad only shows up in Recovery / DFU mode*, and Recovery mode fails with error 4042. Seems like iPad 6 and similar-age devices have been reported multiple times, so I suspect this error is tied to common chipsets of the time. To reach Recovery mode, I plugged directly into a Mac (I happened to use a MacBook Pro 2020 with macOS Monterey 12.6), pressed Power+Home for about 10 seconds, then release Power (keeping Home) for about 6 seconds until the iPad showed in Finder or Apple Configurator (or iTunes on older computers). I had a similar issue happen on an update about a year ago, and it eventually recovered. While DFU failed on multiple attempts, I also continued to keep it plugged in for several days, and at one point it simply booted up on its own. So maybe it's just REALLY sluggish to finalize certain iPadOS updates. The following article may be related, not just because the referenced error numbers are close, but because the behavior is similar: https://support.apple.com/en-us/HT201444