Apple still provides the installer for older operating systems via their support pages. You can download the directly from Apple:
Plug your freshly created El Capitan bootable USB into a working port. Mac Os X El Capitan 10.11.6 Installer Dmg Download
Download OS X El Capitan (Look for the "Use a web browser" section). Apple still provides the installer for older operating
✅ (optional, for security): shasum ~/Downloads/InstallMacOSX.dmg Should equal: b18754e5a484f5f844eea6116b670293fbde8e3b Mac Os X El Capitan 10.11.6 Installer Dmg Download
[Downloaded DMG File] ──> Opens to ──> [InstallOSX.pkg] ──> Runs to create ──> [Install OS X El Capitan.app] Use code with caution.
Click and wait for the process to complete, then close Disk Utility. Step 2: Run the Terminal Command
Select Install OS X from the main utilities menu and follow the on-screen setup prompts. Troubleshooting Common Errors