If you own the movie on physical media or are streaming it, English subtitles are typically built-in.
Finding English subtitles for Donnie Darko is straightforward, whether you're watching a physical copy or looking to download them for a digital file. Official Subtitles (Physical & Streaming)
Standard DVD versions also feature English and Spanish subtitles.
Platforms like Kanopy often provide the movie for free with a library card, complete with subtitle options. Downloadable Subtitles
: A massive community-driven site that is great for finding subtitles for older or rare editions.