This is a custom version of ArduinoCore-mbed which modifies some hardcoded values in variants/RASPBERRY_PI_PICO so that it works with my PCB business card project. It's unfortunate that I need to do this, and that you can't make your own variants without forking the entire thing.
Anyway, I just changed the PIN_LED to 31 since the v3 of the business card does not have a built-in LED, and the pin that it was set to before was 25, which I am using for the Neopixels. This would potentially cause issues because it uses this for USB status indication (which I also disabled). The more "correct" way to do this is probably to create another variant for the business card but I am lazy and it looks like it's a lot of steps to actually do that. I just wanna change one variable, man!
Once I finish v4, this should no longer be needed, since there will actually be a status LED on pin 25 (the Neopixels were moved to 24).