To implement iPA on Facebook for iOS 12.5.5:
Because Meta officially requires iOS 13.4 or later to install the current Facebook application, legacy devices locked out of newer operating systems cannot download it normally. Sideloading a compatible legacy or using specific cloud workarounds are the only reliable ways to restore Facebook access on these vintage devices. The iOS 12.5.5 Compatibility Dilemma facebook ipa for ios 1255
Since you cannot simply double-click an IPA file to install it (as you would an EXE file on Windows), you need a specific tool to "sign" the app and load it onto your device. To implement iPA on Facebook for iOS 12