Using a modern Facebook APK on Android 5.1 (Lollipop) has become difficult because official support for the main app now requires . However, you can still access your account by using lightweight versions or older APK files specifically designed for legacy devices. 1. The Best Solution: Facebook Lite
For users forced to keep Android 5.1 hardware, the following options provide safer or better-performing access to Facebook: apk facebook android 5.1