After setting up the elder router with the correct protocol, I am once again online with the cabled computers. May test the rest later, or replace the usual router. Perhaps not though: It was frightfully hot even before the heat wave. I suspect the heat did it in eventually. It was disconnected from the power grid during the thunderstorm, and the wan cable went through the ADSL modem before getting to it, so it is unlikely that a surge would fry it but leave the modem unharmed.
Anyway, joy joy joy.
But now it is bedtime.