There's a (simple) way to hide or encrypt files and galleries in game directory?
Emphasis is mine
Hmm... Because it can be a mandatory condition for some content (copyrighted music by example), I guess that the, correct, answers gave above need to be weighted:
The fact to group the files into a RPA archive do not mean that the files are protected or unavailable. They'll be out of reach of most players, but most advanced ones will still be able to extract them from the archive.
And, while some dev continue to believe that it worth it, changing the method used to build the RPA, or things like that will not add more protection. It will just limit a bit more the number of people able to extract the content of the archive ; and not even complicate that task.
There's no way to have a Ren'Py game with protected content. Whatever how complicated will be the method you'll use, Ren'Py itself will need to be able to revert it, in order to use the said content. And like Ren'Py is fully made in Python, the user will always have access to that reversion method.
And I really mean "no way". RPYC files can be reverted to their source, as well as PY/PYO ones ; therefore the code will still be available. Even if the said code is obfuscated, it will just be more difficult to understand, not impossible to understand.
At most, you can hide the encryption/decryption method in a library, and therefore have it compiled. But there will be a moment when Ren'Py will have to access it, so to address the library, what will give away the method to access the decrypted content.