For a lot of jailbreakers, AppSync remains one of the most important reason to jailbreak in the first place. With the release of iOS 10, the previous AppSync version only caused a bootloop with lots of iOS devices. We reported this and warned jailbreakers to stay away from AppSync Unified a couple of weeks ago. The good news right now is that a new AppSync Unified version 6.0~b1 has been released and it works with iOS 10 through iOS 10.2.
Contrary to the popular belief that AppSync is only for pirated apps, there are other uses too. For example, emulators are not allowed in the App Store and users have no choice but to install the unsigned ones found all over the internet. Also, it’s very useful when downgrading installed apps.
Although the released version is tagged beta, it looks stable enough as there are no reported issues yet. Be sure to only download from the developer’s repository (https://cydia.angelxwind.net). Other repos may only have outdated versions that might send your device to another bootloop, forcing you to restore through iTunes.