Hi,
Sorry for the late response, I have been working in another project, but I'm planning to add DarknessFall, don't know ETA yet, maybe ChatGPT will do it for me 😂
Now about your error, you should be able to drag and drop the mod inside Mods folder and be able to work, but maybe I need to adapt my project because they changed the mod folder, and it's insde appdata now, need to check how works in vanilla, because I normally play modded versions.