FYI - If I install a fresh Joomla 3.7.3 on php 7.0.1 (or 7.1.7) and install the empty Portfolio template, everything works fine. If I install the quickstart Portfolio on the same configuration, I get a 500 server error on frontend and backend. I have tried:
-Fresh install with Quickstart only
-Fresh install, Installing empty template + Quickstart
-Verified permissions