No way. Fanfics are supposed to be a creative expansion of the original work, but when it comes to 'harry potter harem smut', it not only violates the intended audience of the Harry Potter franchise but also the general standards of good taste. It can have a negative impact on the perception of the Harry Potter brand and can also make the fan community seem less respectful and more focused on inappropriate aspects.
Smut fiction is a type of fictional writing that contains sexually explicit content. It often focuses on sexual encounters, relationships, and desires. However, it is considered a form of adult - oriented literature and may not be suitable for all audiences.
Well, a smut novel refers to a book where the focus is heavily on sexual themes and often has very detailed and graphic descriptions of sexual acts. It's not for everyone and is usually considered more adult-oriented.
One alternative could be creating fanfics focused on untold adventures of the characters. For example, exploring what Harry and his friends did during their summer holidays that wasn't mentioned in the books. Another option is to write about the backstories of minor characters, like how Neville's parents were before they were attacked. You can also create fanfics that revolve around different magical creatures and their relationship with the wizarding world.