Mojave 10.14.3, Safari 12.0.3, Web Clipper updated yesterday.
In those instances when Web Clipper does load in Safari, instead of getting the usual box asking if I want to clip "article," "simplified article" etc, and offering "organization" by notebook, it simply creates a large green box around the entire page with + - at the top and the bottom. I have no idea what that's all about and it doesn't seem to do anything.