I hope you are well today and thank you for your question.
I am not sure what you mean by “auto not showing duplicate posts” so could you please describe it a bit more in detail by sharing your site URL?
For example, you have 3 categories of posts displayed on your homepage, and one of the posts are in all 3 categories. So “the option” will hide the post in 2 posts categories, and displayed only in one category tab. So you will not have 3 the same article on the home page, only one.
Solution for this topic
Currently there isn’t any theme option to achieve this but you can try using different categories or using any of the following solutions.