The milestone 3.1.3 was released on April 30, 2017.
elementaryOS Loki has been added among officially supported distributions. Nuvola flatpaks contain
a work-in-progress GTK+ 3.22 port of the elementary theme to provide elementaryOS users with a native look.
Installation instructions and documentation have been updated accordingly.
All three variants of the Arc theme have been added to Nuvola flatpaks. Issue: tiliado/nuvolaplayer/issues/318