AT module and RN2483: not working with my Linux box

Yes, what you've got there should work. How about totally stripping it back to basics and seeing if anything happens:

var SERIAL_OPTIONS = {
    "rx":B7,
    "tx": B6,
    "bytesize": 8,
    "parity": null,
    "stopbits": 1,
    "flow": null
};
  
Serial1.setup(57600, SERIAL_OPTIONS);
Serial1.on('data', function(d) {
  console.log(">>"+JSON.stringify(d));
});
Serial1.write("sys reset\r\n");

If that doesn't work then perhaps your wiring is wrong? TX should go to RX and vice versa (and obviously you need GND too).

If it does work, perhaps the module itself doesn't send newlines in the way that the AT library is expecting? In that case it might be that the library isn't detecting a newline, so isn't calling the callback with the data.