I am using the GPIO number if you look at my yaml. The input pin for the LED matrix has to be GPIO2/A0/D0 (the upper-left-most pin in the image). I’ve tried “GPIO2”, “2”, and “0” to no effect.
The wiki page specifies “A0” in the Arduino code, though both “GPIO2” and “2” work as well for me (with Arduino firmware):
Getting Started with 6x10 RGB MATRIX for XIAO | Seeed Studio Wiki
Thanks for the suggestion!