Since the certificate is no longer valid, we need to trick your Mac's clock into thinking it's still the past, when the certificate was active.
If you already have an earlier version of El Capitan, you can update to the final version using the 10.11.6 Combo Update . Alternative Sources for ISOs mac os x el capitan 1011 6 iso download gratis work
Look for "Install OS X El Capitan" in your Applications folder. This is the file you’ll use to upgrade or create a bootable USB. 3. Converting to ISO (For Windows/Virtual Machines) Since the certificate is no longer valid, we
Right-click the downloaded InstallMacOSX.dmg and select . This is the file you’ll use to upgrade
If your Mac is compatible, consider installing a newer, still-supported macOS version (e.g., Catalina, Big Sur, or Monterey depending on your hardware) from Apple's official free download.
Select your working El Capitan ISO or DMG file and click OK to begin the burning process. On macOS (Using Terminal)