I had a problem with the latest iOS update too: after installing 13.4.1 it booted to a white screen with „swipe up to upgrade“ at the bottom. Swiping up crashed the device. Every couple of minutes it would reboot and be back to the white screen.

I did a factory reset via finder and that worked. As soon as I restored the iCloud backup: back to the white screen.

I had to revert to 13.4 and could then restore the backup. Now I’m afraid to update again … I guess I’ll have to wait until 13.4.2 or 14 are released. Luckily 13.4.1 does not seem to contain security relevant fixes.