Technically, since RetroArch is available on the iPhone App Store, and RetroArch has the Stella emulator for Atari 2600 games, you can play Yar’s Revenge today. You just need a Yar’s Revenge rom file. You can get that here: Myrient | Content Listing
And many years ago, Atari actually had an app that let you play a catalog of Atari 2600 and other games on the iPhone. Sadly, because it was a 32-bit app, it’s no longer available today, but there was a day where you could play Yar’s Revenge on your phone many years ago.
