I’ve seen a lot of HP fans get kinda mad at J.K. Rowling for not marrying Luna and Neville; for putting Luna with a guy named Rolf and Neville with Hannah Abbott.
I have to say that I do ship Nuna, a little bit. In the books, Luna and Neville, along with Ginny, took care of Dumbledore’s Army when the Golden Trio couldn’t. Some people refer to them as the Silver Trio. Luna and Neville fought alongside each other in many battles. Also–seems like the chemistry between them is just so obvious for some people. Luna, the weird but confident girl with radish earrings, upside down magazine reading, and habits to keep away the Nargles. The perfect lady for Neville, the clumsy boy that sucks at Potions and finds his forte in Herbology, a subject no one really cares about in the books. Luna and Neville are both considered unusual. And apparently, Luna captured Neville’s heart, because there comes a point in which Neville says he’s going to tell Luna how much he loves her because there’s a slim chance she’ll know it after the Battle of Hogwarts, since they could both be dead. Almost everyone thought they would marry.
But JKR said no. Instead, both characters canonically married characters we don’t know very well. However, there is a nineteen year gap between the end of the Battle and the epilogue. A lot can happen in nineteen years, but JKR hasn’t given us much detailed information on what happened during that time. We know that Hogwarts got rebuilt, Romione and Hinny became canon and had kids, Nuna did not because Neville and Luna married different people, Neville started teaching Herbology, McGonagall became Headmistress. Nuna becoming canon would probably make sense if everyone married right after they left Hogwarts. They couldn’t really leave Hogwarts easily anyway, not in the state Hogwarts was in, wrecked by the Battle. We can deduce more information using what we know about the characters, but when we can’t do so anymore, we still do not have a detailed picture of what happened during the nineteen year gap. It’s up to JKR to write a detailed story of it. We can make fanfics, but it still won’t be canon for those purists out there.
So during the nineteen years, something happened that didn’t make Nuna canon–Luna could have friendzoned Neville. Or they went out, but broke it off because Neville found that Luna’s quirks were a bit too alarming for him. Then something else happened that brought Luna with Rolf–possibly the interest in magical creatures and the Quibbler. Meanwhile, Neville somehow got interested in Hannah.
We don’t really know much about Hannah or how she got involved with Neville during those ambiguous nineteen years, so we really have no idea if Neville/Hannah is a good ship. If JKR gives us more information about Hannah and the nineteen year gap, maybe that is when we can decide for ourselves if we like Luna or Hannah better for Neville, and maybe Neville/Hannah could be a more plausible ship. The same goes for Luna/Rolf.