Вы обновляетесь командой

sudo do-release-upgrade

и получаете вот такую ошибку:

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.

Ваша проблема решается простой командой:

RELEASE_UPGRADER_ALLOW_THIRD_PARTY=1 do-release-upgrade