Installing Messenger on iOS 9.3.5 requires obtaining an older, compatible version, usually found through the App Store's "Purchased" history or by using sideloading tools like Sideloadly. Due to server changes, many older versions no longer function, making the web version at messenger.com a more stable alternative.
The most reliable way to get a "solid" working version is to download the directly through your purchase history rather than hunting for potentially unsafe .ipa files online. Use the "Purchased" Method : Open the App Store on your iOS 9.3.5 device. Go to the Purchased tab at the bottom. Search for "Messenger." messenger ipa ios 935 full
If you are stuck on iOS 9.3.5 and need to message friends: Installing Messenger on iOS 9
Getting to work on an older device like an iPad 2 or iPhone 4s running iOS 9.3.5 can be tricky because the official Messenger App now requires iOS 12.4 or later. Because these devices use a 32-bit architecture , they cannot be updated to newer 64-bit iOS versions. Use the "Purchased" Method : Open the App
He finally found it on a dusty corner of the Internet Archive—a legacy version of the Messenger IPA specifically optimized for 32-bit architecture. He fired up his PC, opened an old version of Sideloadly, and connected the iPad. The progress bar was agonizing. 10%... 45%... 90%. Failed. Incorrect signature.