Well, it's not apps that send data, it's your forwarders 😉
But seriously - for data originating on this forwarder, you can just check which inputs are enabled and which are disabled so you can at least verify which inputs are definitely "not needed. Unfortunately, maybe short of some heavy debug, there is not even possible to know which way the event passed through so if you have HF processing data from some set of UF unless you know which UF's are supposed to output to this particular HF, you can't tell it from the resulting indexed event.
Having said that - if you're asking in context of upgrading to python3 and we're talking about HF, you probably mean which modular inputs are in use. I'd just do a btool inputs list and check which ones are enabled.
