Phone would not boot from any starting point
Straight forward - read several articles before starting.
After replacing the motherboard, do a factory data reset so the motherboard recognizes and refreshes the SIM card. After the first power up with the "new" motherboard, started getting "No SIM card - insert SIM card" notices. The FDR took care of that - was able to fully auto activate the phone with Ting.
Great transaction with ifixit - shipped and arrived very quickly - well done ifixit!