> You could encrypt it, but then all the materials are available in memory, so if anyone wants to steal them they just need to look there instead.
> Welcome to the DRM arms race. It's probably not worth the trouble. Copyright law is a better way to protect your resources.
Does Steam adds some layer of protection once we upload the game?
You probably shouldn't worry too much about it really. If you are doing a relatively small indie game - noone would even care to steal any of your assets. I have a game on Steam since 2017 (and working on a second one now) and it has no protection. Can't see any parts of my game anywhere yet.