Preventing iOS/iPadOS system update pop-ups
When Apple issues an update to the iOS, devices show a pop-up alert on-screen over any apps that are running asking if the user would like to update to the latest version. If a user chooses Details, the device redirects out of the app and directly to the main settings menu, which isn't ideal for a kiosk device.
Locking the device to Kiosk Pro using Guided Access or Single App Mode is currently the only reliable way to prevent these update alerts from being shown.