Is there something there that fills the courtrooms with more noble people? Dragonsreach is particularly empty during dinnertime for example. I use Inconsequential NPCS, Interesting NPCS, Populated mods series.

But none of the above actually really fill the room with nobles, apart from Windhelm I believe.

InConNPCs adds foreign envoys to the Blue Palace. But you're right, Dragonsreach is still relatively empty.