Currently the last release of Ubuntu is 19.10 (Eoan Ermine).
We can upgrade from the standard release, or from the LTS. To be sure to upgrade in the release-upgrades configuration file we must check the last line. This line must be:
Prompt=normal
We can update this file with the commands:
$ sudo su
# sed -i -E ‘s/Prompt=(never|lts)/Prompt=normal/g’ “/etc/update-manager/release-upgrades”
Alternatively you have to edit the release-upgrades file in the /etc/update-manager folder, adding the right line.
Then execute:
# apt-get update
# apt-get upgrade
# apt-get dist-upgrade
# do-release-upgrade
Answer yes to the request of upgrade. You will be informed with a prompt about the necessary time.
Voilà tout !