Macbook Pro now has a completely black screen right after install of macOS Monterey

Macbook Pro that was eligible for macOS Monterey now has a completely black screen right after install. Resetting PRAM, Safe Mode, Target Disk Mode -- did not work. Spent time with official Apple support to no end. Macbook boots, but there are no visuals. I can connect over my home network via an older iMac. There were no screen issues before trying the install, no loss of power, no surges, and when attached to the iMac for screen sharing the iMac screen went black too ... so would not seem to be just the screen. What is the fix? Can the Apple store just flash the computer and start over? Can I do anything?