Software installation stuck at the end

To Upgrade from High Sierra will be governed on the Age of this computer. About this Mac will provide the necessary information. With that information in-hand - follow this link How to get old versions of macOS. Once in the next page - you will have to check what version of macOS this computer qualifies to upgrade to. Example for Mojave

Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen and choose About This Mac. These Mac models are compatible with macOS Mojave:

• MacBook (Early 2015 or newer)
• MacBook Air (Mid 2012 or newer)
• MacBook Pro (Mid 2012 or newer)
• Mac mini (Late 2012 or newer)
• iMac (Late 2012 or newer)
• iMac Pro (2017)
• Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with recommended Metal-capable graphics cards)

If you computer qualifies you an download Mojave. Just be sure to only use Safari as Other may not work

Possible issues - an After Market Internal Drive playing up, Not enough Empty Space on the drive - Need at least 10 - 15 GB Empty Space on the drive to allow the expansion of the installer and then to install the upGrade.

If None of these conditions exist on your computer, suggest shutdown computer and disconnect all external drives. Restart and immediately hold the - Shift - key. This is Safe Mode and it will do a Repair Disk, clear cache files and only load Apple Software and Fonts. Now, run the High Sierra installer