How can I upgrade my Mac mini (late 2012) to another update other than the High Sierra?

The Mac Mini Late-2012 can be upgraded to Catalina 10.15.7 but no later than that. See instructions in: How to get old versions of macOS - Apple Support

Back up your data, check your applications for compatibility, and click on Mojave or Catalina.

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Make sure that you have enough room on your hard drive to download and apply the upgrade before proceeding.