Clean Install of macOS 10.11 El Capitan

Installing El Captian is no longer straight-forward.

• download the official installer from here: https://support.apple.com/en-us/HT206886
• create a bootable installation USB drive
• make sure the date is current and correct
• start the installer, this will create the recovery partition
• during reboot, remove the USB drive
• the installation might fail. make sure to set the date back to 2016
• reboot and continue installer
• after subsequent reboot, finish creation of user account
• log in, install udates, done