I've been using Adguard Pro [1], which is paid (not subscription), but open source [2], on my iOS devices. It uses Safari's content blocker mechanism for blocking ads on the web. I went with it over other apps because it supports adding custom rules to block specific elements on a page, like with other desktop ad blockers. If you want to block ads outside of Safari, it can optionally set up a VPN on localhost to block the traffic.
