Personality wise, I think pretty much the same! Very sweet and charming, but intensely focused and closed off.
Beyond that, I think he'd be an extremely physical person - he does so much acrobatics and uses a bow in-game, so I always give him a job that involves a lot of movement - and usually performative aspects - in my fics. (Usually I go with things like dancer/pop star because it's a close parallel to magician, but even pornstar or personal trainer works really well imo). I think he likes to feel present and grounded in his body, and that training can give him a sense of control and power he doesn't have in other aspects of his life.
I also think that his canon childhood shaped him to profoundly that a modern version of him would have to have a similar backstory. I always have him and Wriothesley both as former foster kids - just ones who experienced different situations and outcomes (ie juvie vs trafficking + adoption). This sets Lyney up with the same clear reasons for his protectiveness over Lynette and Freminet and his debt to Arle, and can keep the stakes high (if they need to be, otherwise it's easy to tone down what happened to them to fit the vibe). I imagine Lyney would be really passionate about foster care reforms and helping at-risk youth in a modern context, too. Maybe he'd even do some sort of mentorship program for kids in the arts or something! That's a fun way to work the Hearth in in a less child soldier-ish way.
So yeah! Not sure if you were looking for a guide to how I craft modern AUs in general, but there it is, lol.