Thanks for mentioning Instant View, I hadn't come across that. We actually maintain something similar here: https://github.com/fivefilters/ftr-site-config

We use these in our own tools and also get contributions from others, including Wallabag users: https://github.com/wallabag/wallabag

Before it was sold, Instapaper used to have something similar. A public database of its site-specific extraction templates. We used that as the starting point for our repository.