Designated Survivor: 60 Days - amazing story, very likeable MC and side characters. Romance isn't the focus, the MC is already married at the start of the show, and their relationship is very heathy and supportive of each other. I re-watched it 3 times already :)) - based on the USA Tv Show but the korean one is better in my opinion
Juvenile Justice - law drama, social justice, great characters
Liar Game - there is no romance between the MLs, but their relationship develops in a strong friendship. It's the Korean remake of the Japanese one, and it's based on the manga with the same name.
One Ordinary Day - thriller, mystery, serial killer, amazing relationship between the 2 male leads.
Voice - the 1st season out of 4, with another one on the way. Every season has the same Female Main Character, with the Male character changing between seasons. The is no romance in any season but the chemistry between the characters are great. It has crime, mystery, thirller - a great ride
Through the Darkness - AMAZING, the acting is incredible, it's based on profiling criminals in order to catch them.
Also, if you get bored of kdramas can I recommend you giving a try watching sports animes? There are some that are amazing out there, and I would personally recommend trying: Haikyuu!! - it's about voleyball, has a ton of seasons and the animation is great! Also an amazing main character and also side characters that are marvelous! Although you might suffer afterwards because it's too good :))