Perhaps in this fanfiction, Harry being a male carrier means he is carrying an important prophecy or a magical artifact. He then embarks on a journey to protect it from dark forces who are trying to get their hands on it. Along the way, he might face many challenges and make new allies.
It could also be that Harry as a male carrier has a connection to an ancient magic. This connection causes him to have strange dreams or visions. He starts to investigate these, which leads him to discover secrets about his family's past and his own true destiny. He has to learn to control this new aspect of himself while also dealing with the regular threats in the wizarding world.
One possible plotline could be that Harry, as a male carrier, has some special ability or power that he has to hide from the wizarding world. Maybe it's a power that is not fully understood or is feared by others.
A possible plotline could involve Harry being transported to the world of Alduin and being mistaken for Alduin at first. As he tries to figure out what's going on, he has to learn about Alduin's powers and how to control them. Meanwhile, the real Alduin might be on the loose and Harry has to either stop him or find a way to co - exist with him. There could also be a plot where Harry uses his knowledge from the wizarding world to bring about new changes in the world of Alduin, which might be met with resistance or acceptance from the natives of that world.
One possible plotline could be Harry struggling to accept hugs or physical contact from his friends, causing misunderstandings among them.
One possible plotline could be that Harry somehow gets transported to the world where Izaya exists and they form an unlikely alliance. Maybe they team up to solve a mystery that is plaguing both their worlds.
One possible plotline could be Harry struggling to keep up with his magical training due to his anemia. He might have to find alternative ways to gain strength for spells.
Perhaps Harry becomes a priest to atone for the sins and destruction caused during his battles in the wizarding world. His journey could involve him trying to bring peace and spiritual guidance to a war - torn or troubled community. And along the way, he might face challenges from those who sense his 'different' past.
One possible plotline could be Harry using his vegan lifestyle to promote animal rights in the wizarding world. He might start a club or campaign within Hogwarts to encourage others to be more conscious about their food choices.
One plotline could be Naruto being a transfer student at Hogwarts. He might struggle to adapt to the magic system while also showing off his ninja skills. Another could be Naruto teaming up with Harry Potter to fight a common enemy that threatens both the ninja world and the wizarding world.
One possible plotline could be Harry using his knowledge of the wizarding laws, which he learned through his years at Hogwarts and his experiences with the Ministry of Magic, to defend wrongly accused wizards in a wizarding court. Another could be him trying to reform the wizarding legal system which he might find full of loopholes and biases.
One possible plotline could be that Petunia has a sudden realization of how unfairly she has treated Harry over the years and tries to make amends. She might start by secretly helping him with things around the house or protecting him from Dudley's bullying.
Maybe in a fanfiction, Harry could be framed for something he didn't do, and Snape, believing the false accusations, smacks him in a moment of anger. This could then lead to a series of events where Harry tries to prove his innocence and Snape has to come to terms with his hasty action. Another plotline could be that Snape is under the influence of a dark spell that makes him act out of character, and Harry just happens to be in the wrong place at the wrong time and gets smacked.