Availability can vary by region, but the dubbed version is commonly found on the following services:
Train to Busan is available with an English dub , though its availability varies depending on the platform and region. Apple TV is train to busan available in english dub
Check your local library. Many library systems offer Train to Busan on DVD or Blu-ray for free, and the physical media often includes excellent subtitle quality. Availability can vary by region, but the dubbed