However, on initial load from Arduino IDE I get the following error message:
E (1659) I2C: i2s_driver_uninstall(2047): I2S port 0 has not installed

The Core2 starts without other issues, begins to connect to the network, etc. However, when I actually checked the wayside I could see that the device was creating and deleting a session about every 7 seconds, wierd. When using the AT commands I could see similar OK---OK, --- , OK---OK, etc. In the IoT BASE there is an LED, hard to see from exterior, so I took the case off. From power up I could see almost exactly the same in hardware from the LED on (about 7 secs), off (about 3 secs), and repeat. I can't find anything in the SIM7080G spec that could do this.

My questions are this:
#1 What is the cause of the error message, is it related, and how to solve?
#2 Is the IoT BASE faulty?
#3 Is there another conflict Core2 vs IoT BASE that this is a symptom of?
#4 Does anyone have a working Core2 IoT BASE example I could try?
#5 Have I missed anything else in my ported example from Core to Core2?

// #include <M5GFX.h>
#include "IoT_BASE_SIM7080.h"
#include <PubSubClient.h>
#include <TinyGsmClient.h>
#include <time.h>
#include <sys/time.h>


#define MQTT_BROKER "mqtt.m5stack.com"
#define MQTT_PORT 1883
#define MQTT_USERNAME "IoT_BASE_CATM"
#define MQTT_PASSWORD "IoT_BASE_PWD"
#define MQTT_D_TOPIC "IoT_BASE_CATM/D"
#define MQTT_U_TOPIC "IoT_BASE_CATM/U"  //  上传数据主题

#define UPLOAD_INTERVAL 10000
uint32_t lastReconnectAttempt = 0;

TinyGsm modem(SerialAT);

TinyGsmClient tcpClient(modem);
PubSubClient mqttClient(MQTT_BROKER, MQTT_PORT, tcpClient);

void mqttCallback(char *topic, byte *payload, unsigned int len);
bool mqttConnect(void);
void nbConnect(void);

// Your GPRS credentials, if any
const char apn[] = "soracom.io";
const char gprsUser[] = "sora";
const char gprsPass[] = "sora";

struct tm now;
char s_time[50];

// M5GFX display;
// M5Canvas canvas(&display);

// Module baud rate
uint32_t rate = 0;  // Set to 0 for Auto-Detect

void log(String info) {
  // canvas.println(info);
  // canvas.pushSprite(0, 0);
  M5.Lcd.print(info);
  SerialMon.println(info);
}

void setup() {
  M5.begin();
  iotBaseInit();
  // display.begin();
  // canvas.setColorDepth(1);  // mono color
  //canvas.setFont(&fonts::efontCN_14);
  // canvas.createSprite(display.width(), display.height());
  // canvas.setTextSize(2);
  // canvas.setPaletteColor(1, GREEN);
  // canvas.setTextScroll(true);
  // canvas.println(">>IoT BASE MQTT TEST");
  // canvas.pushSprite(0, 0);
  M5.Lcd.setTextSize(2);
  M5.Lcd.print(">>IoT BASE MQTT TEST");
  SerialAT.begin(SIM7080_BAUDRATE, SERIAL_8N1, IoT_BASE_SIM7080_RX,
                 IoT_BASE_SIM7080_TX);
  nbConnect();
}

void loop() {
  if (!rate) {
    rate = TinyGsmAutoBaud(SerialAT);
  }

  if (!rate) {
    SerialMon.println(F("***********************************************************"));
    SerialMon.println(F(" Module does not respond!"));
    SerialMon.println(F("   Check your Serial wiring"));
    SerialMon.println(F("   Check the module is correctly powered and turned on"));
    SerialMon.println(F("***********************************************************"));
    delay(30000L);
    return;
  }

  // SerialAT.begin(rate);

  // Access AT commands from Serial Monitor
  SerialMon.println(F("***********************************************************"));
  SerialMon.println(F(" You can now send AT commands"));
  SerialMon.println(F(" Enter \"AT\" (without quotes), and you should see \"OK\""));
  SerialMon.println(F(" If it doesn't work, select \"Both NL & CR\" in Serial Monitor"));
  SerialMon.println(F("***********************************************************"));

  while (true) {
    if (SerialAT.available()) {
      SerialMon.write(SerialAT.read());
    }  // else {
    //log("no SerialAT");
    //}
    if (SerialMon.available()) {
      SerialAT.write(SerialMon.read());
    }  //else {
    //  log("no SerialMon");
    //}
    delay(50);
  }
}

void nbConnect(void) {
  unsigned long start = millis();
  log("Initializing modem...");
  while (!modem.init()) {
    log("waiting...." + String((millis() - start) / 1000) + "s");
  };

  start = millis();
  log("Waiting for network...");
  while (!modem.waitForNetwork()) {
    log("waiting...." + String((millis() - start) / 1000) + "s");
  }

  log("Waiting for GPRS connect...");
  if (!modem.gprsConnect(apn, gprsUser, gprsPass)) {
    log("waiting...." + String((millis() - start) / 1000) + "s");
  }
  log("success");
}