A: No mod adds the full Supernova storyline. There is a "Valkyrie" fan-patch that adds content from the previous expansion, but not the story.
Because Fishlabs went radio silent, a dedicated modder known as (from the Steam Community forums) created the unofficial Galaxy On Fire 2 Supernova PC Patch (often labeled v2.1.0 or "Supernova Fix"). Galaxy On Fire 2 Supernova Pc Patch