XIAO nRF52840 + Wio-SX1262 (LoRa-E5?) - Fails to Compile or Join LoRaWAN after Extensive Debugging

Excellent Forum Solutions XIAO
2

Code 1: The final (non-working) RadioLib SPI code

// This code compiles, initializes the radio successfully,
// but the gateway never receives a Join Request.
#include <RadioLib.h>

// ANONYMIZED KEYS
uint64_t devEUI = 0x0102030405060708;
uint64_t joinEUI = 0x0807060504030201;
uint8_t appKey[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

// Pin definitions confirmed from official docs
#define PIN_LORA_NSS  (4)
#define PIN_LORA_DIO1 (1)
#define PIN_LORA_NRST (2)
#define PIN_LORA_BUSY (3)
#define PIN_LORA_RFSW (5)

SX1262 radio = new Module(PIN_LORA_NSS, PIN_LORA_DIO1, PIN_LORA_NRST, PIN_LORA_BUSY);
LoRaWANNode node(&radio, &EU868);

void setup() {
    Serial.begin(115200);
    while(!Serial);
    
    int state = radio.begin();
    if (state != RADIOLIB_ERR_NONE) {
        Serial.printf("Radio init failed: %d\n", state);
        while(true);
    }
    
    radio.setDio2AsRfSwitch(true);
    radio.setRfSwitchPins(PIN_LORA_RFSW, RADIOLIB_NC);

    node.beginOTAA(joinEUI, devEUI, appKey, appKey);
}

void loop() {
    // Fails here with -1101
    node.sendReceive("A", 1);
    delay(60000);
}

Code 2: The simple UART test that FAILS TO COMPILE

// This simple code fails to compile with "undefined reference to 'Serial'"
void setup() {
  Serial.begin(115200);
  while (!Serial);
  Serial.println("Test");

  Serial1.begin(9600);
}

void loop() {
  if (Serial1.available()) {
    Serial.write(Serial1.read());
  }
  if (Serial.available()) {
    Serial1.write(Serial.read());
  }
}