He could meet students from different parts of the wizarding world. There might be some students with really unique magical abilities. And of course, he would meet the teachers at Drumstrang, who would be different from the ones at Hogwarts in terms of their knowledge and how they interact with students.
In this fanfic, Harry could discover new magical creatures unique to Drumstrang. He may also get into some sort of friendly competition with other students. And who knows, he might even learn some new spells that are not commonly taught at Hogwarts. The change of environment would surely have a big impact on him.
In a fanfic where Harry goes to Durmstrang in his first year, he might face a very different educational environment. Durmstrang focuses more on the Dark Arts in some aspects compared to Hogwarts. Harry could be exposed to different types of magic and different cultural views within the wizarding world. He might also make new friends and enemies. For example, he could encounter students who have a more aggressive approach to magic, which would contrast with his more morally - centered views from his upbringing with the Dursleys and his natural inclination towards good. This could lead to many conflicts and also opportunities for growth as he tries to adapt to this new place while still holding onto his own values.
Well, in this fanfic, perhaps Harry struggles with the more strict and traditional rules of Durmstrang. He could be constantly compared to Viktor Krum, who might be a year or two above him. This could create some tension and rivalry. Also, he might discover some secrets about Durmstrang's past that are linked to the Dark Arts, and he has to decide whether to keep them or expose them.
Viktor Krum could be a major character. Since he is from Durmstrang, he might play a role like a mentor or a rival to Harry. Another character could be the headmaster of Durmstrang. He would be important as he sets the rules and tone for the school.
In such a fanfic, Harry's character could develop in many ways. He might become more independent as he has to navigate a new school without the familiar faces of Hogwarts. His views on magic could broaden as he is exposed to Durmstrang's curriculum. For example, he might learn about different ways of dueling that are more aggressive, which could make him more assertive in his magical abilities. Also, his sense of identity could be challenged. At Hogwarts, he was known as 'The Boy Who Lived', but at Durmstrang, he would have to earn his reputation all over again. This could make him more determined to prove himself in a different way than he did at Hogwarts.
Well, he might be able to change some of the bad things that happened. Maybe he could stop Umbridge from being so cruel. He could also be better prepared for the challenges that year brought, like the fight against Voldemort's forces.
Maybe he'll meet a group of magical creatures that are considered mythical in his own world. For example, he could encounter a tribe of centaurs who are more advanced in certain types of magic. They might initially be hostile but then become his allies after Harry proves his good intentions. There could also be a young witch or wizard who has a unique power that Harry needs to complete his adventure.
One interesting plotline could be Harry using his future knowledge to prevent certain bad events from the start. For example, he might stop Draco from becoming a bully right away by befriending him early. Another could be him helping Hagrid avoid getting into trouble with the illegal dragon. He could also use his experience to excel in all his classes from the very beginning and gain a different kind of reputation among the teachers and students.
His relationship with Sirius could be different. He might be more careful and not let Sirius get into danger so easily. Also, his relationship with Hermione and Ron could be strengthened even more as he would be more aware of how important their friendship is.