I could get into the whole Wikipedia page on what dystopian is, but let’s use the Merriam-Webster one. It’s shorter.
an imaginary place where people lead dehumanized and often fearful lives
Regency England on the other hand is known for balls, gowns, overindulgance, and a copious amout of romance books.
What happens when the two mesh together? A dark Regency England, with funeral pyres burning in the countryside, riots in London’s streets, and romance waiting to happen.
It’s not hard to imagine the romance aspect, but the world itself is one of secrets, famine, death, and betrayal.