Is there a reasonable way to get pins 9 & 10 working as GPIO under the Arduino environment? It looks as if the bootloader has to be recompiled, and I couldn’t tell from the docs if this could be done in a way that the board will still work with the Arduino environment.
Never mind. An example exists in the Arduino environment that’s written for the Adafruit nRF52840 Express to convert the pins. It appears to be a one-way conversion from NFC pins to GPIO pins, but I don’t need NFC on these particular boards.