Initially I did a shutdown via the GUI, removed power from the unit, connected the unit to the desired network ethernet, then reapplied power.
During some messaging with @gopher.ny, I got distracted and had left the unit unpowered for 5 or so minutes before powering it on and it seemed to work that time, so all seems well. It appears like the magic sauce was the URL above and doing an extended power cycle, because the initial GUI-initiated shutdown / power cycle didn't seem to set it.
