Several free tools are available that allow users to restore their iOS devices using unsigned IPSW files. Here are a few:
Before using any tool listed below, the user must understand the limitations:
Limited. FutureRestore works on Windows but requires saved blobs. For checkm8-based restores, Windows support is poor – use a Linux live USB or macOS VM.
Tools like FutureRestore are free but require technical knowledge and pre-saved SHSH blobs.