Originally Posted by
J. D. Guy
As Restingvoice mentioned, Duke is the lead of the We Are Robin series, and we learn a lot about his personal self there.
As well, we learned details about Duke here and there, some visual inference and some in supplimentary materials.
For example, his debut in Zero Year showed his room. We can see that among other things, Duke is into pen-and-paper RPGs/tabletop RPGs. We Are Robin's lead-in hype included a character bio that notes that Duke's drive and motivation is internal, rather than external like some people's are. This was in reference to his athletics and academics. As well, while he doesn't get the space to showcase and explore this side of himself, he is said to be into "geeky" hobbies. Duke also has writing talent, in prose and especially in poetry, though he is noted to keep that latter side of himself to himself.
His inquisitive and empathetic nature, which we do get to see of Duke and which is one of his defining traits, leads into the possible speculation that he may have gone in his mother's footsteps and become a social worker like she was prior to the Endgame storyline. This last part is my own introspection of Duke's character, though it's based on what we learn of Duke and his mom in Snyder's All-Star Batman backups and the Batman and The Signal mini.