There could be a fanfiction where the Dursleys read the books secretly. As they read, they are filled with a sense of dread as they realize how horribly they've treated Harry all these years. This self - realization leads to a series of internal and external changes within the family.
Some Harry Potter - themed fan communities on social media platforms might also be a source. For example, on Reddit, there are sub -reddits dedicated to Harry Potter fanfiction. You can post a request there asking for 'Dursleys read the books' fanfictions, and the community might be able to point you in the right direction.
One interesting Dursleys fanfiction could be about Dudley's life after learning the truth about the wizarding world. Maybe he starts to have a change of heart and tries to make amends for how he treated Harry over the years.
One popular fanfiction might be about the Dursleys' secret past that somehow ties them to the wizarding world in a more complex way. For example, perhaps there was a wizard in their family line long ago that they've been trying to hide. Another could be a story where the Dursleys have a change of heart much earlier than in the original series and start to embrace Harry's magical nature, leading to all sorts of comical and heartwarming situations as they try to understand the wizarding world. And there could be a fanfiction where the Dursleys are forced to face the consequences of their mistreatment of Harry in a more magical and extreme way, like being haunted by magical apparitions that represent Harry's pain.
One interesting fanfiction could be about the Dursleys having a change of heart before Harry goes to Hogwarts. Maybe they start to see the magic in him in a different way and struggle with their newfound feelings of protectiveness. It could show a different side of the usually cruel Dursleys.
There might be a fanfiction where the Dursleys are actually related to a minor wizarding family in some convoluted way. This discovery could lead to a whole new set of adventures and relationships for them. They could be dragged into a wizarding mystery that forces them to cooperate with Harry and other wizards, which would be a huge change from their usual behavior of trying to avoid all things magical.
They would probably be horrified. The Dursleys are very set in their ways and the strange and often unorthodox ideas in fanfiction would be too much for their narrow - mindedness.
There are quite a few. One popular one is 'The Protector's Grace' where a powerful wizard steps in to rescue Harry from his miserable life with the Dursleys.
Some fanfictions might depict the Dursleys as having a more complex relationship with Harry. They could be in a situation where they have to protect Harry from a greater threat, which makes them put aside their differences. For example, a dark wizard could be targeting Harry, and the Dursleys realize that their home is the safest place for him at the moment, so they have to work together with Harry to keep him safe.
There are indeed fanfictions that give the Dursleys a positive spin. In some, they might be forced to face the reality of the wizarding world in a more profound way. This could lead to a transformation in their characters. Maybe Petunia remembers her sister more fondly and decides to be kind to Harry. Vernon could also come around and see that Harry's abilities can be an asset rather than a threat. These fanfictions often explore different paths for the Dursleys that deviate from their strictly negative roles in the official Harry Potter series.
They are popular because the Dursleys are such complex and disliked characters in the original series. Fanfictions give readers a chance to explore their motives and potentially redeem them. For example, we can understand why they treated Harry so badly in some fanfictions which might be due to their fear of the unknown world of magic.