Mac Os X 10.11 El Capitan Iso Download -

Once you have the official InstallMacOSX.dmg or the Install OS X El Capitan.app:

# Create a blank CDR image
hdiutil create -o ElCapitan -size 8g -layout SPUD -fs JHFS+
If you or anyone in your family downloaded El Capitan when it was current (2015-2018), it remains in your Apple ID purchase history.
An ISO works, but a direct USB installer is better. Use the same createinstallmedia command but point to a USB drive (e.g., /Volumes/MyUSB) instead of a DMG.