I have a MacBook Pro 13 Mid-2009 5,5 that I need to install El Capitan. The drive is erased. I have a more recent MacBook Air with Mojave installed and an assortment of external HDDs and USB drives. I’ve tried several things, including the CreateInstallMedia thing in Terminal, but that doesn’t find something it’s looking for and croaks. I’ve tried installing El Cap onto an external drive, but I’m told I can’t install OS X because Mac OS is not installed (?). So yeah.