Same problem here with iPhone X after upgrading from 13.4 to 13.4.1 yesterday.
Here's what I found out and a solution (at least if you have a backup):
- Connect the phone to a Mac and put it into DFU/recovery mode
- For me, this only worked on a Mac! My Windows PC didn't recognize the iPhone X in DFU mode!
- So, I used iTunes on a Mac to freshly install iOS 13.4.1. After that the iPhone did work again but the "swipe up to upgrade"-error re-occured after I recovered my iCloud backup!
- What now? The solution was to downgrade to the previous version of iOS:
- I got the package for iOS 13.4 from https://ipsw.me and used this manual to install it
- iPhone restarted fine and recovering the latest backup from iCloud also worked!
So, there seems to be something wrong with 13.4.1 that makes some phones crash. I'm a little worried that I'll be stuck with 13.4 for the rest of my iPhone X's life now... @apple, any idea? I have a first gen iPhone X. Is the reason maybe some setting for accessing the control center when the screen is locked? On the other hand, the phone keeps on restarting so there must be something else wrong.