Are you guys looking into Mutant Year Zero? It is a fun sandbox rpg with 4 expansions already. The expansions all happen in the same world, but each has a different feel set in the post apocalyptic world. I would love a sound set that lets my group start at their mutant ark and take a trek to Mechatron 7 which would switch from a fall out wasteland feeling to a more cavernous in the vault feeling.
There’s quite a few sets already in existence that could fill in for that. In the Sci-Fi player there’s Cyberpunk Hot Zone (and you could add Avernus from the Fantasy Player for crazy vehicle chases, if that’s a thing in Mutant Year Zero), and then Sub-Terra or Mi-Go Underground Dwelling for a cavernous feel. What sorts of sounds/creatures/events/other places are needed for Mutant Year Zero? I can certainly recommend what sounds might be already here for you!