House has central heat again. Bought a replacement control board. Naturally is showed up the day I was leaving for a week long trip. Got back yesterday, installed today.
I bought a used board from Amazon. Higher risk of a bad replacement but it was exactly the same model/part number. New replacement boards are now apparently a universal design with adapter wire bundle...a complication I chose to avoid. Plus they cost 3-4 times as much ($2-300 v $69).
The LED on the new board is on steady like the old board used to be. Apparently the rapid flashing LED on the old board was a pathetic cry for attention rather than any useable indication of onboard diagnostics.
Another adventure in home repair completed successfully. (fingers crossed)