.h file for class

#ifndef TestClass_h
#define TestClass_h

#include "Arduino.h"
#include <M5Unified.h>

class TestClass {
  public:
    //-- Define RS458 to UART to UART2, HardwareSerial needs a UART number passed to it --

    //What I have tried, I would like to hardcode the UART number to 2. How do I do this?????
    HardwareSerial SerialRS485; // 1 - Does not compile, I need something in the .cpp file to make this work
    HardwareSerial SerialRS485(uint8_t _uart); // 2 - Can get this to compile but then does not compile if I use a uncomment the test funciton
    HardwareSerial SerialRS485(uint8_t 2); // 3 - Does not compile

    //constructor
    TestClass();
      
    //Functions - Main
    void testFunction();


  private:
    uint16_t _private1 = 0;

};

#endif

.cpp file for class

#include "TestClass.h"
#include "Arduino.h"

//Constructor def
TestClass::TestClass() {
}

void TestClass::testFunction() {
    Serial.println("USB Serial Port");
    SerialRS485.println("RS485 Serial Port");
}

main ino file

#include "Arduino.h"
#include <M5Unified.h> //For M5Stack ESP Hardware

//Create test class
#include "TestClass.h"
TestClass TestObject;

void setup(void)
{
  auto cfg = M5.config();  //M5 Unified config
  M5.begin(cfg);
  delay(500);
}

void loop(void)
{
  M5.update(); //Update button state
  TestObject.testFunction();
  delay(1000);
}