Unplug printers, external hubs, USB drives (except backup drive), and even second monitors. Only keep your mouse, keyboard, and backup drive attached.
To update from macOS High Sierra 10.13.6 to macOS Catalina 10.15, you will need to download the installer directly from the Mac App Store, as it won't appear in your standard "Software Update" settings wikidot wiki 1. Check Compatibility
Unplug printers, external hubs, USB drives (except backup drive), and even second monitors. Only keep your mouse, keyboard, and backup drive attached.
To update from macOS High Sierra 10.13.6 to macOS Catalina 10.15, you will need to download the installer directly from the Mac App Store, as it won't appear in your standard "Software Update" settings wikidot wiki 1. Check Compatibility how to update macos high sierra 10.13.6 to 10.15