Can client IP address be obtained from Arduino Ethernet2 library for W5500 during client.connected() call?
Use the new update of the 'old' Ethernet library. It is version 2.00 and you can install or update it in the Library Manager in IDE. Note, it is not Ethernet2 library. The new Ethernet library supports W5500 and has client.remoteIP().

example 

  if (client.connect(server, 80)) {
    Serial.print("connected to ");
    Serial.println(client.remoteIP());





  New features in version 2.0.0
  Auto-detection of W5100, W5200, and W5500 Ethernet hardware.