Stop iOS auto-downloading updates
Solution 1:
iOS 12 actually sped-up iOS devices all around! I highly recommend you upgrade.
However, if you really don’t want to upgrade for personal reasons, you can install the tvOS provisioning profile for tvOS pre-releases on your iOS device. This should block iOS updates as your phone will be configured to fetch tvOS upgrades, but tvOS updates are not compatible with iOS devices.
Solution 2:
If you've already turned off Updates in iTunes & App Store and deleted the update in Manage Storage, then your final option is to totally block the update domains
https://appldnld.apple.com
https://mesu.apple.com/
in your hotspot. This will block all software updates to any device connected to the hotspot. [1]
However, a variety of reliable sources (NY Times, USA Today, WSJ, Associated Press) would recommend updating to iOS 12. Many of them cite speeding up older devices as the primary reason.
Solution 3:
How can I stop iOS from automatically downloading updates?
iOS/iPadOS 13.6 has introduced the ability for users to turn off automatic download of updates. To configure automatic download or installation of iOS/iPadOS updates on your iPhone or iPad, go to Settings app → General → Software Update → Customize Automatic Updates and toggle the switches as desired.
The linked Apple Support document discusses the same:
- https://support.apple.com/kb/HT204204
Customize Automatic Updates
With iOS 13.6, or iPadOS, you can choose not to download software updates automatically. Go to Settings > General > Software Update > Customize Automatic Updates, then turn off Download iOS updates.
