Telephoto with GCam can work...but not without effort. First, you need root. Second, you need that root access to replace a system library file with a patched one. Since a patched library file is needed, it means that with every system update, you need a new patched library. Probably not worth it for most, but if you are already rooted, could be worth a try. I don't have the Exynos model, but this file should work for the AUDA build ROMS.