iMac needs to be upgraded from High Sierra
Google is telling me, along with some of my banking websites, that I need a newer version of MacOS. My model is late 2013 21.5 inch. When I go to the look for updates, none show in the App Store. Can I still upgrade to Mojave or Catalina like the articles I've read state?
iMac 21.5″, macOS 10.13