[cyclecount]

Every release is an LTS version, with support for about 8 years.

The current stable release of macOS (10.14 Sonoma) supports all Macs introduced in 2017 and later.

[luuurker]

Older macOS versions don't receive all security fixes, so while you'll receive security updates from time to time, the OS isn't fully patched. It's a bit different from, say, Ubuntu LTS.