Estas são as mensagens de erro:
Err:1 https://esm.ubuntu.com/infra/ubuntu xenial-infra-security InRelease
Could not resolve host: esm.ubuntu.com
Err:2 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu xenial InRelease
Temporary failure resolving 'ppa.launchpad.net'
Err:3 http://ppa.launchpad.net/ubuntu-desktop/ubuntu-make/ubuntu xenial InRelease
Temporary failure resolving 'ppa.launchpad.net'
Err:4 https://esm.ubuntu.com/infra/ubuntu xenial-infra-updates InRelease
Could not resolve host: esm.ubuntu.com
Reading package lists... Done
W: Failed to fetch http://ppa.launchpad.net/deadsnakes/ppa/ubuntu/dists/xenial/InRelease Temporary failure resolving 'ppa.launchpad.net'
W: Failed to fetch http://ppa.launchpad.net/ubuntu-desktop/ubuntu-make/ubuntu/dists/xenial/InRelease Temporary failure resolving 'ppa.launchpad.net'
W: Failed to fetch https://esm.ubuntu.com/infra/ubuntu/dists/xenial-infra-security/InRelease Could not resolve host: esm.ubuntu.com
W: Failed to fetch https://esm.ubuntu.com/infra/ubuntu/dists/xenial-infra-updates/InRelease Could not resolve host: esm.ubuntu.com
W: Some index files failed to download. They have been ignored, or old ones used instead.
Responder1
Passo 1. Verifique a sua conexão com a internet. Se estiver ruim, mude para um espelho local. Verifique também se o seu dispositivo está configurado corretamente para se conectar à Internet.
Passo 2. remova todos os PPAs e tentesudo apt update && sudo apt full-upgrade
Etapa 3. tente alterar manualmente xenial
para bionic
in /etc/apt/sources.list
e todos os arquivos em etc/apt/sources.d
e depois sudo apt update
. Eu não tentei isso antes porque esse é o "jeito debian", mas deve funcionar. Embora, por precaução, você deva fazer backup de seus arquivos.