The original soundtrack to Year Unknown is now available for free on Steam and Bandcamp:
https://store.steampowered.com/app/3331890/Year_Unknown_Soundtrack/
https://julianheuser.bandcamp.com/album/year-unknown-ost
Both releases include lossless audio, as well as Music for Exploring Megastructures, a 35 minute ambient track made of new and unused music.
I hope you enjoy!