I got Nuclear throne in the bundle for racial equality, meaning that it didn't come with a steam key. Is there a way to play this mod or use it without owning the game on steam?
You would want to throw in some steam_api.dll so that it doesn't complain on start, or, possibly, rename/remove Steamworks.gml.dll, which is what references steam_api.dll. See any topic discussing use with Epic Game Store version for reference.