There are many reasons that users don’t want to update their device to latest iOS versions. For example, some people want to stay their device on specific version to wait for an upcoming jailbreak, or app developers want to test their app on a legacy iOS version …etc.
Before Feb. 2020, the most convenient way to block OTA update is installing a tvOS beta profile. However, since iOS 12.x (I’m not sure the specific version), iOS checks whether the profile can be installed in current device. Thus, tvOS 13 beta profile can’t be installed on iOS 12.x and above, and tvOS 12 beta profile has been already expired since 31/1/2020.
So, this tutorial provides some methods, which can let you block OTA for any device on any iOS versions.
If you want to post this tutorial to other place, please refer to this post, thanks!