This is presumably an str dongle, in which case no kplex doesn't decode that but can take output from programs which do (aiscatcher, rtl-sdr...). The script you reference above for starting aiscatcher shows it broadcasting output on port 10110 on the loopback interface (127.0.0.1). You could add an interface to kplex to capture that:
"port" is unnecessary given 10110 is the default but you might want to change that to something else in the aiscatcher startup and kplex config to simplify other configuration.
A little googling found someone who seems to be using rte-sdr to do something similar with a different-but-apparently-functionally-similar dongle: