AdGuard has many products that "works on" iOS.

The main app is a glorified localhost VPN (it runs a basic VPN-like server locally and redirects all the traffic through the app, allowing for DNS based filtering). This uses the official AdGuard servers and allows for no configuration whatsoever.

One step better is taking the time to grab their DNS profile for iOS which allows for DNS based filtering without the VPN app constantly running.

An even better step to take is to use the AdGuard DNS service - it's basically like a hosted version of AdGuard Home, but it's paid, limited in queries and devices, on the other hand you have control over the blocking (add exceptions, custom blocklists, rules and so on). This service allows setting up different "servers" (rulesets) you can assign to different devices, and everything is controlled from one interface, which is nice.

And the best is what I do, self-hosting AdGuard Home with custom blocklists, and a privacy focused approach (AGH serves as my local DNS resolver for my home network and VPNs over port 53, and 443 with a Caddy proxy in front for DoH outside the network, with a secret subdomain approach per device so only my own devices can abuse my DNS server).

Then there's the browser plugin based filtering that literally looks at the incoming HTML and picks out the ads. That unfortunately does not work with either Chrome or Firefox on iOS.