How does one download El Capitan from the App Store using High Sierra The link from Apple's support page redirects to the Mac App Store but upon clicking download you're met with an error message saying you "This version of OS X can't be installed on the computer" 
Note: I've tried 4 different MacBook Pro TouchBar but none will download it. 
I'm only looking to download El Capitan so I can create a USB installer for an older Mac.
If the older Mac has a recovery partition, there are three different key combinations you can use to select different O.S. versions to install from internet.

If it doesn't have a recovery partition, you might still be able to use Internet recovery.