Pli999 Said:
“How to update El Capitan to High Sierra: Hi all. I want to update my MAC 2011 from El Capitan to High Sierra in order to run Office 365 but I can't find a lint in App Store to High Sierra. Now all links lead to Catalina which can't be installed in my Mac.“
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Use a USB Bootable Installer:
First: Back up your Mac with Time Machine - Apple Support
Then...
Install with a USB Bootable Installer. Go here, and select the code for High Sierra (macOS 10.13). Use a USB Flash Drive of 16GB for this. The Link: How to create a bootable installer for macOS - Apple Support. Use another Mac to create this Installer, if using this Mac is of no success. Of course, ask whomever for permission to use their Mac, if not yours :)