You can now root the Galaxy S4 on Lollipop. You won't even trip knox. You will need to download a specific fimware, and supersu. You will also need to download and install Mobile Odin on your S4. You won't be able to do this without an external sdcard which could be a bummer if you don't have one. You will need to run Mobile Odin on your phone flashing the firmware and check the option for everroot. The process is super easy. Head to the link below for the full guide and download files.
via XDA