Meta has become aggressive with "App not supported" warnings. When you log into the old version, you will likely see a yellow banner at the top of your feed stating:
Paper uses a stripped-down, text-first interface. It loads incredibly fast on A7 and A8 chips (iPhone 5s and 6). It handles news feed reading far better than the main Facebook app's old version. facebook old version for ios 12.5.5
If you have previously downloaded Facebook using your Apple ID, it will be in your purchase history. Open the on your iPhone. Tap your Profile Icon (upper right corner). Select Purchased . Search for "Facebook." Tap the Cloud icon with the downward arrow. Meta has become aggressive with "App not supported" warnings