user42159: I can use the serial-over-USB channel by simply using Serial in my code.
The LoRa32u4 has an RXD1 and TXD1 pair on pins 20/21 (Arduino 0/1).  

https://docs.bsfrance.fr/documentation/11296_LORA32U4/LoRa32u4_pinout_diagram.pdf
How do I configure and use this serial port (for receiving NMEA GPS)?

user368: 
[ATmega32U4-based boards use] Serial1 to communicate via TTL (5V) serial on pins 0 (RX) and 1 (TX). Serial is reserved for USB CDC communication. For more information, refer to the Leonardo getting started page and hardware page.


42159: <p>I can use the serial-over-USB channel by simply using <code>Serial</code> in my code.</p>

<p>The LoRa32u4 has an RXD1 and TXD1 pair on pins 20/21 (Arduino 0/1).  </p>

<p><a href="https://i.stack.imgur.com/lM0iY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lM0iY.png" alt="enter image description here"></a>
<a href="https://docs.bsfrance.fr/documentation/11296_LORA32U4/LoRa32u4_pinout_diagram.pdf" rel="nofollow noreferrer">https://docs.bsfrance.fr/documentation/11296_LORA32U4/LoRa32u4_pinout_diagram.pdf</a></p>

<p>How do I configure and use this serial port (for receiving NMEA GPS)?</p>
 368: <blockquote>
  <p><a href="https://www.arduino.cc/reference/en/language/functions/communication/serial/" rel="nofollow noreferrer">[ATmega32U4-based boards use] Serial1 to communicate via TTL (5V) serial on pins 0 (RX) and 1 (TX). Serial is reserved for USB CDC communication. For more information, refer to the Leonardo getting started page and hardware page.</a></p>
</blockquote>
