Try a force restart > press and quickly release the volume up button > press and quickly release the volume down button > press and hold only the side/power button (do not slide to power off) for 15-20 seconds until the screen goes black and a white Apple logo appears and then release the side button.

This is a known bug, You have to skip through the beginning until you get to the Home Screen. From there do the update under settings and once it updates, Then do a factory reset and then do the transfer.