I think this is usually a stupid answer, but maybe the documentation will help you a little.
https://docs.blender.org/manual/en/latest/grease_pencil/modifiers/generate/line_art.html
Have you tested the occlusion and intersection functions from the modifier yet?
If not, it seems like you could use face mark filtering. Then you can set the edges manually but i have no idea either, the topic is new to me. i just want to help
