I get what you mean, I also hate that there is romance in every drama (I mean, it's like they have to force some romance in there even if it does not fit the story line) ... so, I think it is really hard to find a drama without romance. I am always trying to look for dramas that do not have that much romance or where romance is just a "subplot". That's why I love historical dramas the most, because romance is often not the main story line and that's great :) .. so, if you like historical stuff I'd recommend you to watch Queen Seon Deok. It's one of the best drama's I've ever seen and I'm rewatching it at the moment. Well, to be honest there is some love involved, but they don't get together and love really is not a big part oft the story. You should check it out! (Don't be scared by the large number of episodes, it is a good watch and not boring at all).
Also, the Three Musketeers was a really good show without much romance and it is pretty short (I think it was 12 episodes). Honestly, I could have watched more episodes, because it was really good.
I also really liked Shut Up Flower Boy Band (that's not a historical drama). There is romance, but it's not really a big part of the story.
School dramas are also good, because there is not always a romance story or it is just on the sidelines, but I saw on your list that you've basically watched most of them already^^
Maybe you want to try one of those, I guess I still could find some more, but it's not that easy to find dramas without romance/with litte romance :(
... I had to edit, because I didn't see that you don't like angsty things (I really like angst, but not paired with romance) and I somehow recommended dramas which involve angst (I think Three Musketeers is the most lighthearted one of those). Still, maybe you like one of them :)
