Success! Removing the wrong library (188) allowed a successful compile. I had already installed the correct library (13) for a another project. What happened here is that I did a ‘pio lib search Adafruit_GFX’, saw 188, and installed it. The prior library is found with ‘pio lib search Adafruit-GFX’.
So as UI suggestions:
• It would be good if near-match text strings were also returned for searches and shown together.
• It would be good if the search results noted when you already have the library installed.
BTW, I have to say that the fact that this is the only trouble I’ve had shows how awesome PlatformIO is!