Before hunting down a Viber .ipa for iOS 4.2.1, understand the implications:
Why jailbreak? iOS 4.2.1 has excellent jailbreak tools (greenpois0n, redsn0w). Jailbreaking allows you to bypass signature checks and install any .ipa using tools like iFunBox or iPhone Explorer.
Steps:
Instead of hunting for a non-functional Viber .ipa, consider these alternatives that still work (or can be made to work) on iOS 4.2.1:
To understand why a specific .ipa is required, let’s review Viber’s compatibility: Viber .ipa for ios 4.2.1
Key takeaway: You need Viber version 2.1.2 or earlier. Any version above 2.2 will likely crash on launch or refuse to install due to missing frameworks (like JavaScriptCore or LocalAuthentication).
iOS 4.2.1 was released in November 2010. It was the last supported version for the iPhone 3G and the iPod touch 2nd generation. Before hunting down a Viber
Viber launched its first iOS app in December 2010. The very first Viber versions (1.0.x) were indeed compatible with iOS 4.x. However, these versions are now over 14 years old. Viber has since moved to a modern architecture that requires iOS 11 or later.
If your goal is simply to use your old iPhone as a communication device, Viber might be a dead end. Consider these alternatives that work better on legacy iOS: Instead of hunting for a non-functional Viber