Apparently it has been 4 years since I tried to use an Arduino, because 4 years ago I posted: "Is programming an Arduino from macOS always a nightmarish clusterfuck, or am I just lucky?" and I still have all the same questions as last time.
Dear Lazyweb, can someone please tell me what chickens I have to bleed to make macOS 10.14.6 and Arduino IDE 1.8.13 talk to an Adafruit Metro Mini? It says "/dev/cu.ARPT: Resource busy". System Info shows a TUSB3410 connected, but maybe that's something else, I can't tell.