Its a little hard to find a solid romance centered drama with no love triangle but the ones that come to mind are: Healer, Thousand Days Promise, Goblin, Descendants of the sun, high end crush, Eccentric Daughter In Law, Noble My Love, Hogoo's love (there is a love triangle or love square but it was rooted in misunderstanding only), I am Happy, ode to joy (season 1 and 2), surgeons
Other dramas with no real love traingle (....but I personally didnt like): High Society (though the second couple was just adorable, School 2017 (the main couple was cute but the story was disappointing), oh my venus (I just could not get into this drama), somehow 18
There are those dramas that have a pretty weak or forgettable second lead that it seems pointless to really make it into a love traingle. (.... or more like a a nuance/small character that like the main leads much like Love O2O): Fight My Way, Reply 1997, All about Mom, Marriage Contract, Queen Inhyuns man, W: Two worlds, Fantastic, because its my first life
Great dramas with no love triangle but its not a drama centered on romance : romantic doctorkim teacher, Tunnel, circle, witch's court,
