I have installed opensky feeder on Rasperry Pi where I have FR24 feeder too. Opensky feeder is connected to dump1090 at port 30002 but no data is receiver by the feeder. I think is the correct port because others applications like VirtualRadar o PlanePlotter connects properly with Beast protocol to this port and all it's ok.
As you can see on log, connection to opensky network is ok and the feeder is online, but my receiver is offline on my receiver profile on opensky web. Maybe because there is no data to send?? There are two warnings that I don't know if they are important. Some private data have been replaced by XXXX.
Ok, change it to 30002 again (sorry, I missed you wrote that other feeders work on that port).
Then wait for ~10 minutes, the feeder writes some statistics into the log. Maybe I can see something from there.
I just discovered that your dump1090 is sending the AVR raw format, e.g. "@016CE3671C745DFFE7AB7BFCAB;".
This is NOT the binary beast protocol, which the feeder expects.
You are either using an incompatible dump1090 branch or you have not enabled the beast binary protocol (I think it's the "--net-beast" option).
That is the key, engel, thank you very much. I discovered that fr24feed starts dump1090-mutability with options that make Beast protocol port is not open.
I dont know how to change that, so I have connected another SDR device and I have started other instance of dump1090-mutability that open port 30005 for Beast protocol, and my flights are now arriving to opensky-network page.