For the most reliable "download" (physical ownership), you can find remastered Blu-ray sets on sites like Amazon. These often include high-quality English dubs and original Japanese audio.
If you want to "own" a digital copy to keep on your device permanently, you can purchase individual episodes or full seasons from: Download Digimon Episodes and Movies
Most major streaming apps allow you to download content directly to your mobile device or tablet for offline use: For the most reliable "download" (physical ownership), you
