iPhone is stuck and won’t restart with a hard restart

(1) Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:

• Press and quickly release Volume UP button
• Press and quickly release Volume DOWN button
• Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF). 

(2)  If the above does not work then - Follow the instructions in this article by Apple ➔ If your iPhone is Non-Responsive or Frozen and see if that helps.

Axel F.

I am having this same problem as well, but with IPhone 11. It keeps getting stuck at the very end of the update and not finishing. I am going on 8 hours now with 4 forced restarts and nothing has worked :(