Unofficially, each major version of macOS gets a year’s full support, with bug and security fixes, then 2 years of security updates. Is that how it works?
Setting up a new (or repurposed) Mac: 7 Choices diagrammed – The
Mac Troubleshooting Summary – The Eclectic Light Company
Postscript – The Eclectic Light Company
Virtualisation on Apple silicon – The Eclectic Light Company
Making the leap from Mojave to Apple silicon – The Eclectic Light
MacOS partition concerns - Apple Community
Mints: a multifunction utility – The Eclectic Light Company
When the Finder's error exceeds 50% – The Eclectic Light Company
Last Week on My Mac: A quiet word about help – The Eclectic Light