Freezing of iPhone when software updated has been tapped
Why does my iPhone 8 Plus freezes when I tap software update on settings
iPhone 8 Plus, iOS 13
Do you have a VPN or other kind of Wi-Fi firewall enabled, which blocks the contact to Apple servers?
Did you try to update on your computer?
Update your iPhone or iPad - Apple Support
If this does not work, have a look at the troubleshooting mentioned here:
If you can't update or restore your iPhone or iPod touch - Apple Support