https://www.pcgamer.com/fallout-4-project-valkyrie-is-a-huge-20-quest-mod-that-adds-new-game-endings/

Not only does Fallout 4's Project Valkyrie mod add 20 new quests and a handful of dungeons, bunkers, and player bases to the Commonwealth, it lets you alter the base game's ending. 

Out now on Nexus Mods, it's billed as an expansion for similar player-made projects Fusion City Rising and Outcasts & Remnants, and it looks like this: