Lineart for grease pencil objects

Hi guys!
I’m trying to find a way to make the lineart for my character. The thing is, it’s a grease pencil object, and when I try to apply the lineart modifier, it doesn’t work.

You can see, that even when viewing from camera, the lineart just doesn’t appear.
I tried using some visual effects, like shadow, but it’s not really what I need.

I tried using freestyle lineart, and it works completely fine with 3d usual object, but not with my character.

Is there anyway to make lineart for a grease pencil object in blender? I even tried to look for some addonsm but didn’t find anything, and even on the internet I haven’t seen anyone with a similar problem.

What do I do? I really need this for my work.

I need your help!