Yes, there might be. The world of fanfiction is vast and full of crossovers. Fans often like to combine different fictional universes, so it's very possible that someone has created a story where Harry Potter is a fan of Madara Uchiha. You can search on various fanfiction platforms to find out.
There are several places. First, as mentioned, FanFiction.net and AO3 are the most popular. But also, some Reddit communities dedicated to fanfiction or to either the Harry Potter or Naruto fandoms might be helpful. You can post a request there asking if anyone knows of such a fanfiction. Additionally, Tumblr has a large fan community, and you might be able to find relevant fanfictions or at least get some leads on where to find them. When searching, be specific with your keywords and also be prepared to look through a fair amount of unrelated content before you find what you're looking for.
Well, perhaps the plot could involve the main character having the powers of both the Harry Potter world and being the heir of Madara Uchiha. They might use Sharingan - like abilities to see through magical illusions in Hogwarts. And they could combine ninjutsu with magic, for example, using a fire - based ninjutsu spell to fight dark wizards.
A plot could involve a magical experiment gone wrong that merges the essence of Madara Uchiha with the magic of the Harry Potter universe. This creates a new being that has both the powers of the Sharingan and wizardry. Harry Potter and his friends then have to figure out how to deal with this new entity. Is it a friend or a foe? Madara's memories and desires start to influence the new being's actions, leading to a complex situation where the line between good and evil is blurred.
The main character could be someone who was accidentally transported from the Naruto universe to the Harry Potter world as a baby. Growing up in Hogwarts, they have no idea about their Uchiha heritage until certain events start to trigger memories or abilities. They would be a unique character, having the innocence of a Hogwarts student but also the latent power of an Uchiha. Their friends at Hogwarts would help them uncover their true identity, and they would have to learn how to use their Uchiha powers in a world that is completely new to them.
Madara's Sharingan would be a very unique ability in the Harry Potter world. It could be used for things like detecting lies, seeing through invisibility spells that are not as advanced as the Sharingan's capabilities, and predicting an opponent's moves in duels. His ability to use fire - based jutsu could be seen as a form of very powerful and different magic. Also, his physical combat skills would make him a formidable opponent in a world where most rely on wands for combat.
One interesting storyline could be how Fem Harry Potter's magic interacts with Madara Uchiha's Sharingan abilities. Maybe her magic could enhance or disrupt the power of the Sharingan in unexpected ways. Another could be their cultural clashes, as Harry comes from the wizarding world and Madara from the ninja world. They might have different values and ways of doing things, which could lead to both conflict and growth as they learn from each other. Also, a possible plot could involve them teaming up against a common enemy that threatens both their worlds, like a powerful dark force that combines magic and ninja techniques.
Often, Naruto might be paired with Madara in some sense. Their opposing views on power and peace could create interesting interactions in the fanfiction.
No. Naruto has his own unique story and character development that is distinct from simply being a fanfiction of Uchiha Madara. Naruto is about his journey to become Hokage, his relationships with his friends like Sasuke, Sakura, etc. His goal is to bring peace to the ninja world in his own way, through understanding and friendship. While Madara is an important part of the Naruto lore, Naruto's story is not centered around being a fanfiction of Madara. He is his own hero with his own dreams and challenges that are not directly related to being a fan of Madara.
No. Harry Potter is a distinct and original wizarding world created by J.K. Rowling. It has its own unique magic system, characters, and storylines that have no relation to the Uchiha concept from Naruto. The two are from different fictional universes with their own identities and fan bases.