How to use AppSync Unified to sideload apps on your iDevice [iOS 2.1.1 - 16.5.1]
[1] Add the cydia repo cydia.akemi.ai
[2] Tutorial for iOS 2.1.1 - 2.2.1. Be careful, as you can brick your device.
'Appsync for OS 3.1' from eatmyphone.github.io/deb for iOS 3.1
'Appsync for OS 3.2' from eatmyphone.github.io/deb for iOS 3.2
'AppSync 4.0' from cydia.akemi.ai for iOS 4.0-4.2.10 / 4.0-4.3.5
'AppSync Unified' from cydia.akemi.ai for iOS 5.0-16.5.1
[3] Download AppManager.
[4] You’re done! Sideload apps to your heart’s content. Some good ways to find IPAs are thru iOSOBSCURA on archive.org.
Have fun!