Responses
Tbh, I'm not quite sure if they're dukes but I remember them being historical manhwa.
https://www.mangago.zone/read-manga/beta_count_so_has_changed/
https://www.mangago.zone/read-manga/spinel_baekji/
https://www.mangago.zone/read-manga/who_s_your_daddy/
https://www.mangago.zone/read-manga/solar_eclipse/
The flower of Aloshya
Bl recs with dukes? Like the mc or the ml is the duke