Same problem here. iPhone 12 mini. Updated to 14.5.1 and lost cellular data but WiFi works fine. Oddly though, the Ookla speed test app shows cellular data working as expected, but no other apps can find the internet.

Also, tried all the resets. Including reset all settings -still no dice. I guess I’ll be backing up erase all content/settings restoring next. Ugh what a paaaaaain