The GoPro 5, 6 and 7 do not support an analog microphone input via USB-C anymore.
However GoPro does offer a Pro Mic Adapter for those GoPro models. 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, 6 or 7 like you are used to do with a GoPro 3/4.
- set your Tentacle to output level MIC
- connect your Tentacle with the provided black mini jack cable to the Mic input of the adapter
- connect the adapter to the USB port of the GoPro
Here is the link to the GoPro Pro 3.5mm Mic Adapter