No! A "no installation candidate" error can also happen if you are trying to install a package that is only available to a later version of Ubuntu. One way to solve this issue is by using Ubuntu backport, a special repository where users can submit and maintain an up-to-date version of a package for older versions of Ubuntu. It can be helpful if an upgrade is unwanted, but the latest software is needed. You can install a package through backports by using the "-t" option in apt followed by the name of your Ubuntu version and "-backports."