No computer needed. Super fast. Works with your existing subscription. Cons: You can only watch it inside that specific app. If you cancel Netflix, you lose the movie. The file is often protected (DRM), so you cannot move it anywhere else.
Find a movie in the Disney+ app and tap the icon below the play button. You must reconnect to the internet at least once every 30 days to keep downloads active. Apple TV App can you download movies to ipad
Go to Settings > App > Download Quality on Netflix or Disney+ and select "Higher Quality" if you have space, or "Standard" to save storage. No computer needed
Always test one download before you leave the house. Put the iPad in and try to play the movie. Some cheap streaming apps have bugs where they try to "verify" your account even though the file is local. Cons: You can only watch it inside that specific app