I baulked at the $25 price as much as anyone else would, so I used the free desktop app, and web app which works on mobile (ankiweb.net), for a month. After that, I was happy to pay $25 to support the developer and get the ability to edit cards on mobile and work offline.
The AnkiDroid app for Android is free, and is basically a reimplementation of Anki with compatible behaviors, storage formats and configuration. It's a complete, self-contained Anki implementation; it does not require anything on a desktop computer.
https://apps.apple.com/app/ankimobile-flashcards/id373493387
It looks just as dodgy as “doctors hate this one weird trick”, and costs a ton up front. Why would I believe something like that?