There is a firmware bug in Mac OS 12.3 that renders the update impossible to install on any 2021 14 or 16 inch MacBook Pro that has had it's logic board replaced. The cycle is: You try to upgrade, the upgrade will fail but recovery to handle it correctly, you'll reboot still on 12.2.1 but with a report a problem dialogue informing you of an iBoot Panic You'll try to upgrade again. This time, the iBoot FW will corrupt. You'll see the apple icon flash on boot 5-6 times before seeing the exclamation mark symbol telling you recovery is needed. You can try and revive using a second Mac with Apple Configurator 2. This will fail, because it tries to load the 12.3 firmware from the IPSW, in either DFU or Recovery mode. The only way to get things running again is to manually download the 12.2.1 IPSW and use Apple Configurator 2, with the Mac in DFU mode, to load the revive image. This will update the firmware of iBoot, and the recovery image to a working build. The Mac will then restore 12.2.1's OS, keeping your data upon finishing. I've submitted as many logs of all this to AppleSeed via Feedback Assistant, but I suspect this will take days to actually get to someone to can acknowledge the issue. In the meantime, there's going to be many bricked MBPs as most people won't have a second Mac to preform a revive, and even if they do, won't understand why that fails as it tries to load 12.3. There's seemingly no point going to the Apple Store Genius Bar based on @sfriedrich's comments. They'll just do a logic board replacement again which will fail on upgrade.