[BenTheElder]

Do you know if any browsers are doing this?

In practice on iOS nothing seems better than safari + the content rules for adblocking, but I admittedly didn't try every app

Shipping your own content lists seems like a tricky way to differentiate since users could install similar lists without using your browser.

aside: It also appears to just inject CSS you have to inject it via javscript now which feels a bit gross but certainly doable.