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Sungkyunkwan Scandal (gender bender! strong bromance, or
is it a bromance?)
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A Tree with Deep Roots (a king created new alphabets, which made almost everyone apoplectic; one of the best historical Kdramas out there, IMHO; light on romance)
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Secret Investigation Record (Joseon X-files; no romance, though)
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Six Flying Dragons (about the founding of Joseon Dynasty; again, light on romance)
Stuff with more emphasis on romance (I haven't personally watched them, but they seem to be popular):
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The Princess' Man-
Empress Ki-
Jang Ok JungFrom your plan-to-watch list,
Arang and the Magistrate and
The Moon that Embraces the Sun seem to be quite well-regarded by people who have watched them.