Sadly the GoPro 5 does not support an analog microphone input via USB-C anymore.
However GoPro does offer a Pro Mic Adapter for the GoPro 5. This dongle style adapter is not perfect in terms of size, but together with a Tentacle it can be used to record timecode on a GoPro 5 like you are used to do with a GoPro 3/4. The adaptor is nearly as big as a Tentacle, so it’s not a perfect solution. But we have tested it and it will work.
Hope that helps!