To expand a bit on chrisbeardy's response: The SENDER_AMS you use in add_route_to_plc, should be different than the AMS Net ID that is defined internally on your PLC(for you that would have been '5.97.120.143.1.1').

So, when adding a route in your PLC using add_route_to_plc(AKA the route from PLC to linux) use a self defined AMS Net ID(6.97.120.143.1.1 for example). If you use the AMS Net ID of the PLC here(5.97.120.143.1.1). Then you are basically telling the PLC to send data to itself.

You should ONLY use the AMS Net ID of the PLC(5.97.120.143.1.1) when setting up an connection from Linux to the PLC with pyads.Connection()