It's a bug affecting most a14 users. If you force reboot the phone, the screen starts working. Fix lasts maybe a day?
Set your phone to auto reboot daily and wait for a fix. Sadly that's kinda all I can suggest.
Also of note, an iPhone would cost maybe 5-10 times as much as an a14. If you were going to do that, just get a better A series device. My personal belief is that the a14 isn't powerful enough to handle the update. An a56 would be plenty fast and cheaper than any iPhone