I had the printer tilted over, so here's a pic of the Duet WiFi with PT100 4-wire interface.  Luckily there were was a convenient 4-pin connectorized portion of the ribbon cables going to the top end, so I was able to hack in the four wires cleanly all the way to the hot end.  The wiring is a bit of a mess, due to length limitations from the original (RAMPS) controller.

Note the solid state relay is actually bolted to the case.  :)