Serial Information is incomplete and misleading

[KurtE]

https://www.arduino.cc/reference/en/language/functions/communication/serial/

Particularly the Arduino GIGA. As for example you say Serial1 19(RX1) 18(TX1)
When actually the RX1, and TX1 pins are used on the Serial2 object... And you don't mention anything about Serial4.
From your cheat sheet you see:
https://docs.arduino.cc/tutorials/giga-r1-wifi/cheat-sheet/#serialuart-pins

Serial.begin(9600); //initialize serial communication over USB
Serial1.begin(9600); //initialize serial communication on RX0/TX0
Serial2.begin(9600); //initialize serial communication on RX1/TX1
Serial3.begin(9600); //initialize serial communication on RX2/TX2
Serial4.begin(9600); //initialize serial communication on RX3/TX3

Not sure if you have same issue with DUE?

Also there are issues with other boards that have native USB:

Leonardo, The Serial object is native USB, and Serial1 object is pins 0, 1.

UNO R4
Serial is USB
Serial1 is on Pins (0, 1)

WIFI: 2 other Serial objects talk to ESP32 (one for USB to Serial, the other for WIFI and BT)

On both of them you can create another Serial object on pins 18, 19)
On Wifi: Serial3 is logically defined as UART4 which is not implemented, but you sketch can
define the object:

UART _UART4_(18, 19)

Likewise MINIMA you can define Serial2 with the UART2 object.

There are probably other issues.

[karlsoderby]

Hey @KurtE , there are definitely some inaccuracies to be updated in the table inside on the page you linked. Legacy boards such as the UNO R3 (AVR) share the 0 & 1 pins with the USB serial port, but for most new boards with native USB this is not the case.

We will try update this in the near future, thanks a lot for reporting the issue.