Note: This only works with iOS 13.1 and later. Earlier version of iOS do not recognize external drives in Files. For earlier versions of iOS you need to use Giradman’s suggestions. Special drives with companion apps. (sub note: some of these apps are not playing well with iOS 13.
Ok, a couple of caveats first. I’m using an iPad Pro with a USB-C port, so no guarantees. I’m using a multi-port USB-C adaptor. Older iPads may need a less power intensive adaptor. Apple’s own should work.
What you need.
1) Lighting to USB adaptor, or thumb drive with a Lightning port. Be aware than most current lighting port drives need and require a companion app to work. Newer ones, in anticipation of iOS 13, may not.
2) The drive itself. Be sure it works with the iPad by doing some research. Some drives, especially with older iPads, draw too much power and the iPad won’t work with them. Not a problem with the iPad Pros.
Plug in the thumb drive and confirm it is showing up in the Files app. Go to Photos, select the photos you want, In the Share menu scroll down and find Save to Files. The mounted USB drive should show up at the bottom of the list.
To automate the task, say to photos older than some date, you could try using the Shortcuts app, Find Photos and Save File actions. I did a quick test using Select Photos instead, and it worked (but slowly).
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