If you're tired of iDevice's update notification in iOS 12(it also works on earlier iOS version), 3uTools will help you out. After you successfully installed the description file, iDevice’s system won’t detect iOS updates anymore, and it won’t download the firmware, either.
Step 1: Run the latest 3uTools on PC. Connect iDevice to PC using the USB cable. Find and click “Stop iOS Update".
Step 2: Ensure iDevice is unlocked, then click “Send Description File to iDevice" to install it on iDevice.
Step 3: Click“Install" -> enter power-on password. And then just follow the tips to continue your operations.
If you can’t view the page below after installing it successfully, please find it in Settings-> General-> Profile-> tvOS 11 Beta software profile.
Step 4: After restarting iDevice, a "Feedback" icon should be on iDevice.(Except jailbroken iDevice under 9.x)
This icon can't be deleted, you can hide it in a folder on your device.
You should see the current iOS is up to date.