https://www.pcgamer.com/sakhalin-is-an-ambitious-fallout-4-story-mod-inspired-by-new-vegas-and-stalker/

Fallout: Sakhalin is an ambitious Fallout 4 mod that adds a new island, with new interiors, quests, factions and monsters. 

Inspired by New Vegas's DLC and GSC Game World's Stalker, Sakhalin Island is set within an alternate Fallout universe future, whereby remnants of Communist China, The USSR, Imperial Japan and Nazi Germany seek treasures on the eponymous archipelago.