Mailing the story:

Ubuntu 21.10 comes out today, an interim release with nine months of support, and the first to use GNOME 40 for the desktop. The Ubuntu release cycle delivers a new LTS (Long Term Support) version every two years, the next one being 22.04 in April. This means that 21.10 is a handy preview of features that may not get production use until 22.04.