> but for actual browser apps, content blockers are sorely missing.

A simple, but functionally very basic app that does ad-blocking on iOS is Firefox Focus. This might cover most people's basic privacy needs, but not as a fully-functioning experience (I use this more for 'one-off' site visits, where I don't want to be tracked, see ads, or have any persistent record of my visit on the device).

But for a fully-featured browser with user-configurable content, JavaScript, CSS and ad-blocking, then the little-known iCab Mobile[0] does almost everything that a desktop browser can do in terms of privacy and content-control.

[0]https://apps.apple.com/us/app/icab-mobile-web-browser/id3081...