I still haven't received an answer to my question. Will the mods that are ALREADY created for this game only work with the steam version?
As was initially said, you can safely ignore that error you posted here.
As for "mods" not working, what does the log say afterwards/beforehand? "Plugins loaded 0" (or something similar)?
In which case, you simply never added a plugin (mod) for bepinex to load, or atleast not correctly.
Considering that there didn't seem to be any other error messages, I reckon you just never added the plugins correctly, or what you wanted to add is not actually a bepinex plugin, as such bepinex does not care for the file(s) in question.
In case it does show plugins to load, but no further error messages, nor anything you expect it to do:
Ensure you understand the mod in question correctly as to what it does, whichever it may be.
From the little I could gather, the information you do provide for your issue is heavily limited, so we can't really help you out much. Worst case, try getting in contact with the mod developer in question, who may or may not be able/willing to help.
As for mods utilizing the official "mod support", I reckon you probably won't have much luck getting them without owning the game on steam and using steam workshop to download them (or steam cmd logged in with an account that owns said game)
