The best solution on iOS is Yattee. You can add Piped or Invidious instances as locations and stream ad-free YouTube from there. Another solution that doesn’t involve Piped and Invidious is AdGuard. Open a YouTube link in Safari, hit actions, then hit Block YouTube Ads (by AdGuard).
You can try Yattee for YouTube. It’s in the AppStore, you just need to give it an invidious or piped instance to connect to.