Naruto Shippuden is a licensed property. The complete series, especially the English dub, is a premium product. While you can easily stream it, downloading permanent, high-quality copies requires legitimate purchases or subscriptions with offline features.
If you have a Crunchyroll subscription:
To help find the exact platform or setup that works best for your offline viewing setup, let me know: Download All Naruto Shippuden Episodes English Dubbed
Download the Hulu app on a supported mobile device, find Naruto Shippuden, and tap the "Download" icon next to the episode. 3. Netflix Naruto Shippuden is a licensed property