He would probably become an even more powerful ninja. With the Ultimatrix, he could transform into various alien forms, each with their own unique abilities. This would give him an edge in battles against tough opponents like Madara or Kaguya. He could use the alien powers in combination with his ninja skills, for example, using an alien form's strength along with his Rasengan technique.
If Harry Potter got the Ultimatrix in fanfiction, it would be a total game - changer. He might start using the alien forms in his battles at Hogwarts. Imagine him turning into an alien that can fly during a Quidditch match, giving Gryffindor an unbeatable advantage. Also, the magical world would be both fascinated and a bit scared of his new powers. Some might see him as a threat, while his friends would support him in exploring the new abilities the Ultimatrix gives him.
Sorry, I don't know the precise cancellation date. Maybe it was cancelled because of financial reasons or a shift in the target audience. Try doing a search on popular entertainment websites for the accurate information.
His relationships with his friends might change a bit. His friends would be both amazed and maybe a little bit intimidated by his new powers. For example, Sasuke might see Naruto as an even greater rival now. And his relationship with his sensei, like Kakashi, would also be different as Kakashi would have to help Naruto understand and control these new alien powers.
It's a story that likely involves the concept of 'the Force' which is central in Star Wars universe. It probably follows the adventures of characters who can manipulate the Force in different ways.