iPhone 12 Pro Repeatedly Disconnects While Attempting Restore

iPhone 12 Pro, iOS 17

MacBook Pro, OS 12.1

iPhone suddenly turned black with spinning dial. After several minutes, went to Apple logo. That screen continued to come and go for hours. Multiple attempts to force restart failed. Connected to MacBook, entered recovery mode. Walked through steps to update. Failed repeatedly. Forced to restart MacBook repeatedly to get software downloaded to register. iPhone stays connected for 15 minutes and then disconnects/unmounts. When I re-enter recovery mode, the download no longer has a status bar, but by clicking another finder item then returning to phone, a gray barber pole appears and remains. I am able to see the download in Activity Monitor. When it finally (once) got to "extracting software," it crashed and issued and error message that the firmware was corrupted.

Things I have already tried so please do not suggest:

I am using factory Apple cable USB-C to lightning, that is never used except for this purpose. I tried 2 other cables just in case.

I have tried all four USB ports.

Everything is plugged in. No apps are running.

I already spoke to Apple support, they told me I had already done everything.

I have used exclusively Apple/Mac since 1983 so I am very familiar with the devices and systems.

The restriction of the iPhone staying connected for just 15 minutes at a time makes it so it is literally impossible to repair/restore on your own. Clearly intentionally designed as part of the ever-increasing dedication to planned obsolescence. The inability to manually download a software update to the MacBook and THEN update/restore the phone has infuriated me to the point of ditching all Apple devices (we have 12) and going Android. If anyone has ANY suggestion, please let me know. Thanks!