Have you tried viewing your iCloud keychain on macOS? I'm not sure if it's inclusive of entries made from iPhone-only apps, but there's definitely an option to view entries synced to iCloud for other things.
Have you tried viewing your iCloud keychain on macOS? I'm not sure if it's inclusive of entries made from iPhone-only apps, but there's definitely an option to view entries synced to iCloud for other things.
I think I tried that a long time ago, including various tricks to see the hidden folders on the iPhone file system, but it didn't work.
Now I'm not going to install any FB-related app on my new phone to test any other ways, because I'd rather not let them mark that device too if I can help it.