Rules can be updated dynamically using updateDynamicRules.

I wrote an extension that implements declarativeNetRequest redirects to private front ends just using a static hardcoded list. It only took a couple of hours. I’m using it on MacOS and iOS. I don’t think it’s the kind of thing that would take significant investment from the developer, I just don’t think they have any plans or motivation to make it more private than the current implementation.

Also, TIL about URL rewrites! Now all of my search results use private frontends. Thanks for the tip!