If you're looking to download OS X El Capitan 10.11, you can find it on the Mac App Store. However, please note that Apple no longer supports this version of the operating system, and it's recommended to upgrade to a newer version of macOS.
It's always recommended to download software and operating systems from official sources, such as the Mac App Store or Apple's website. os x el capitan 10.11 download dmg
Are you currently using a to create the bootable drive? I can give you specific commands to fix it. El Capitan full installer - Apple Support Community If you're looking to download OS X El Capitan 10
Connect your USB drive. Open Disk Utility , select the drive, and erase it using Mac OS Extended (Journaled) formatting, naming it "ElCapInstaller". Are you currently using a to create the bootable drive
Apple hosts legacy operating systems for users with older hardware. You can download the official DMG via this Apple Support link: