The addon accessed some freestyle render settings through the active render layer. with the way blender data access (collections, etc.) changed, the api call to access the active renderlayer changed. When I enabled the addon, it raised an error when the code used the old api call. I had to change bpy.context.scene.render.layers.active.freestyle_settings to bpy.context.window.view_layer.freestyle_settings on those lines to get it to work.
here’s the error message the broken code would produce.
(I’m honestly a python beginner; I’m only good at fiddling with the python console and reading api references, so excuse my bad explanation. I have used this addon since I fixed it so I’m pretty confident it works now.)