There's also a possibility that it could be a drama genre. Given that it's based on a true story, there are likely to be conflicts, emotions, and relationships that can be explored in a dramatic way. The chevalier's story could be full of tension, whether it's in his personal life or in the events he was involved in, which are all elements of a drama.
It could be a historical genre. Since it's based on a true story about a chevalier, it will likely involve historical events, settings, and characters from the relevant period.