I'm not sure if there is such a specific fanfic. Fanfics cover a wide range of themes and scenarios, but this particular one seems rather unorthodox. It might exist in some corner of the vast fanfic universe, but it's not a common or widely known concept.
It would be a very strange and unorthodox take on the characters. Aragorn is typically seen as a noble and just leader, and Boromir is a proud warrior. This scenario would completely change the dynamic between them and might be seen as a form of discipline in a rather odd context within the story.
Boromir might develop a sense of wonder. Earth has so many different cultures, landscapes, and technologies. This exposure could make him less rigid in his thinking. He could start to question the way things were in Middle - earth and consider new ways of living. He might see how different races interact here in a more peaceful way compared to the tensions in his own world and strive to bring that back to Middle - earth if he ever returns.
He could meet Frodo. Frodo is a very important hobbit, and Aragorn might have an interesting conversation with him about the Ring and their different experiences.
Aragorn may develop a more complex relationship with power. As the Ringbearer, he has to constantly battle the allure of the Ring's power. This could lead to him becoming more humble as he realizes how easily power can corrupt, even someone as strong - willed as him. He might also grow in his understanding of the smaller races, like the hobbits, who he now has a new - found respect for since he is in a position similar to Frodo's.
Talion might be in awe of Aragorn at first. Aragorn is a well - known figure in Middle - earth, a rightful king. Talion, being more of a lone warrior, could look up to Aragorn's leadership. Aragorn, on the other hand, would likely be cautious yet curious about Talion. He might question Talion's methods which are different from his own. But as they get to know each other, they could develop respect for each other's skills.
One common theme is redemption. Since Boromir's character in the original story had some flaws and made mistakes, in these fanfics where he lives, he often gets the chance to redeem himself. For example, he might make amends for his actions regarding the One Ring.
One great 'boromir x reader fanfic' is 'The Unseen Bond'. It beautifully captures the essence of Boromir's character and his relationship with the reader. The story is filled with adventure and emotional depth.
Sure, there are. The great thing about fanfiction is that it allows for all kinds of wild combinations. In 'Harry Potter Boromir' fanfiction, perhaps Boromir becomes a part of the Hogwarts faculty. He could teach combat skills or something related to his own experiences in Middle - earth. You can often find these by searching for specific tags on fanfiction platforms.