I know this seems like a FAQ, but I promise I did a reasonable amount of research -- also, I've had it working many times in the past. Doesn't mean I've not done something stupid though.
So, got a new Mac laptop (Sierra installed) and went to rebuild my FLORA dev environment by installing the latest IDE (1.6.13) and follow the directions for getting the contributed boards added.
Placed this URL in the preferences:
https://adafruit.github.io/arduino-board-index/package_adafruit_index.json
Then, opened up the Board Manager and selected "Contributed" from the drop down, and there is only one that shows up "Windows 10 iOT core" -- the AVR stuff doesn't show up. So I select "All" again, and AVR is actually the top one (See attached screenshot). Note the text for that one does not mention the FLORA board.
And when I drop down the Boards menu, no FLORA (see attached screenshot).
Again, I am totally open to the idea that I have done something stupid, so no need to be gentle with me.
Thanks for any thoughts or insights.
Cheers,
Ron