Apple still provides the El Capitan installer for those who cannot upgrade to newer versions.
To download OS X El Capitan 10.11.6, you can get the official disk image directly from mac os x el capitan 1011 6 iso download gratis work
: Hosts several versions for archival purposes, including the full 10.11 installer GitHub Repositories : Some users maintain collection links for macOS ISOs specifically for virtual machine users. Internet Archive System Requirements Apple still provides the El Capitan installer for