How to make main chunk updater in game

So i had really stupid idea of making a project where i would have multiple horror stories (like DLCs) in game and player after installing the game will have one downloaded and others will be downloaded during runtime if player wants and i would overtime add more of those DLCs but now im not sure how would i do it because im broke so i won’t upload game on steam so i won’t have luxury of having launcher that will be able to update main chunk of the game so is there any way i could have game validate if the main chunk file is the same one as the one on firebase (or some other cloud storage server) so i can update the game that way even tho i dont know how would i update the chunk than if the file with the same name is in use because of the game running