Note: Some pins are not connected on a standard Arduino Uno R3 but still listed so you can use them if you had a custom board. It might also be possible that your ICSP header of the 16u2 is flipped ...

In this review of the Maker Uno RP2040 board with the Arduino IDE we could blink LEDs, control RGB LED lights, press the user button to turn on one LED or make the buzzer output some melody, control a ...

Note: Some pins are not connected on a standard Arduino Uno R3 but still listed so you can use them if you had a custom board. It might also be possible that your ISP header of the 16u2 is flipped 180 ...