Naruto would need to train harder to make up for the lack of an arm. He could develop new jutsus or modify existing ones. Maybe he would start using more wind - based attacks that can be controlled with just one arm and his chakra control. Also, his friends might help him by creating prosthetics or assisting him in battles.
Sasuke could be a candidate. Given their complex relationship, Sasuke might find a way to give Naruto a new arm as a way to atone for their past differences. He could have discovered some rare medical ninjutsu during his travels or come across a powerful artifact that he uses to create a new arm for Naruto.
Maybe Orochimaru. Despite being a villain in the past, he is a master of forbidden jutsus and experiments. He could see Naruto as an interesting subject and give him a new arm with some dark powers, which Naruto would then have to learn to control for the greater good.
Well, Naruto might rely on his other senses more. His sense of smell, which is already quite sharp, could be enhanced further. He could also use his chakra to sense the environment around him, like how he can detect the presence of others. And he'd probably train with his friends more, especially those like Hinata who can guide him using her Byakugan.
Well, one possibility could be that Naruto gets a new arm with some special abilities. Maybe it was given to him by a powerful ally or he discovers an ancient artifact that attaches to him as a new arm. This new arm could have powers like enhanced strength for his ninja techniques or the ability to sense danger more acutely.
Well, Naruto might adapt to Shunpo in the fanfiction by first observing. He's good at that. He'd watch how others use it, break down the movements in his mind. Then he'd practice, using his determination. His chakra control, which he has improved over time, would also play a role. He'd likely infuse his own style into it, not just copy it blindly.
Naruto might adapt by using his ninja skills. His ability to quickly learn and adapt in his own world would help him in the Familiar of Zero world. He could use his stealth and combat skills to survive and make his place.
He might rely more on his other senses like hearing and smell. Just like real - world blind people can develop enhanced other senses, Naruto could use his chakra to sense the environment more acutely.
Naruto adapts by using his determination. He's used to facing challenges in his own world, so he applies the same mindset in the new world. He also tries to learn about the new culture and rules quickly. For example, if the new world has a different form of combat, he observes and practices.
Well, perhaps the new arm comes from some kind of ancient and mysterious source. It could be an arm that was once part of a powerful ninja from the past. This new arm could have a mind of its own, at first causing Naruto some trouble as he tries to control it, but eventually they work in harmony and it gives Naruto an edge in battles against tough enemies.
Well, it could be that he got it as a gift from some super - advanced ninja technology group in the fanfiction world. Maybe they saw his need for an extra weapon or tool during battles and decided to equip him with a metal arm.