Nuvola 4.9 was released on December 17th, 2017. It is mostly a maintenance release as most of energy is invested in the Chromium port of Nuvola and the development of other features has slowed down. The current status of this ambitious effort will be described in a separate announcement.
Note that Nuvola versioning has changed after Nuvola 3.1.3 and version 3.1.x became 4.x (3 + 1 = 4).
--webkitgtk-supports-mseif it isn't true.