When I try to upgrade from Ubuntu 19.10 (Eoan Ermine) to Ubuntu 20.04 (Focal Fossa) I get the following message:

Invalid package information

After updating your package information, the essential package 'ubuntu-minimal' could not be located. This may be because you have no official mirrors listed in your software sources, or because of excessive load on the mirror you are using. See /etc/apt/sources.list for the current list of configured software sources.

In the case of an overloaded mirror, you may want to try the upgrade again later.

Why does this happen since it should be a normal procedure? I want to change that animal soon. ;)

Askify Moderator Edited question April 16, 2023