I didn't see any specifics as to what Ubuntu you installed.
Ubuntu Server is a server system and only has terminal or CLI (command line) input. Releases of this product are year.month in format, ie. Ubuntu Server 21.10 is the 2021-October release (add 2000 to the year).
Ubuntu Core is another type of server system, ie. again only text terminal or CLI options (it's intended for headless operation). Releases of this product are year in format, ie. Ubuntu Core 20 is the 2020 release (again add 2000 to year). There are differences to these specialist releases, thus why the different format is used for releases (also only one release is made in a year so need for month)
Ubuntu Desktop has a GUI; as it's intended for use on desktop or laptop type of computers; it's the only Ubuntu that provide GUI or graphic interfaces. Ubuntu also has flavors which are variations of the base Ubuntu Desktop system with different GUIs. Releases of these products use the year.month format, so the latest releases will be Ubuntu 21.10 or the 2021-October release.
You may have installed a Ubuntu Server product that doesn't have a GUI (graphical user interface) system, ie. one of the server choices. Providing full details of what you installed allow better understanding of where you are, and the ideal fix.