merci à vous deux pour les réponses et explications
je n'arrive à tout sélectionner d'un coup dans le terminal, je colle en plusieurs parties
ThinkPad:~$ cat /etc/apt/sources.list ; cat /etc/apt/sources.list.d/*
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://fr.archive.ubuntu.com/ubuntu/ focal main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://fr.archive.ubuntu.com/ubuntu/ focal-updates main restricted
# deb-src http://fr.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://fr.archive.ubuntu.com/ubuntu/ focal universe
deb http://fr.archive.ubuntu.com/ubuntu/ focal-updates universe
# deb-src http://fr.archive.ubuntu.com/ubuntu/ xenial-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://fr.archive.ubuntu.com/ubuntu/ focal multiverse
deb http://fr.archive.ubuntu.com/ubuntu/ focal-updates multiverse
# deb-src http://fr.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://fr.archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu xenial partner
deb-src http://archive.canonical.com/ubuntu xenial partner
deb http://security.ubuntu.com/ubuntu focal-security main restricted
deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu focal-security universe
deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu focal-security multiverse
deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
# deb http://ppa.launchpad.net/captiva/ppa/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/captiva/ppa/ubuntu xenial main
# deb http://ppa.launchpad.net/diesch/testing/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/diesch/testing/ubuntu xenial main
# deb http://ppa.launchpad.net/nextcloud-devs/client/ubuntu focal main # désactivé pour la mise à niveau vers focal
# deb-src http://ppa.launchpad.net/nextcloud-devs/client/ubuntu bionic main
deb http://ppa.launchpad.net/nextcloud-devs/client/ubuntu bionic main
# deb-src http://ppa.launchpad.net/nextcloud-devs/client/ubuntu bionic main
# deb http://ppa.launchpad.net/nextcloud-devs/client/ubuntu focal main # désactivé pour la mise à niveau vers focal
# deb-src http://ppa.launchpad.net/nextcloud-devs/client/ubuntu bionic main
# deb http://ppa.launchpad.net/noobslab/macbuntu/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/noobslab/macbuntu/ubuntu xenial main
# deb http://ppa.launchpad.net/noobslab/macbuntu/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/noobslab/macbuntu/ubuntu xenial main
# deb http://ppa.launchpad.net/noobslab/macbuntu/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/noobslab/macbuntu/ubuntu xenial main
# deb http://ppa.launchpad.net/noobslab/themes/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb http://ppa.launchpad.net/noobslab/themes/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb http://ppa.launchpad.net/noobslab/themes/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb-src http://ppa.launchpad.net/noobslab/themes/ubuntu xenial main
# deb http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu xenial main
# deb-src http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu xenial main
# deb http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu xenial main
# deb-src http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu xenial main
# deb http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu xenial main
# deb-src http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu xenial main
# deb http://ppa.launchpad.net/varlesh-l/papirus-pack/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/varlesh-l/papirus-pack/ubuntu xenial main
# deb http://ppa.launchpad.net/varlesh-l/papirus-pack/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/varlesh-l/papirus-pack/ubuntu xenial main
# deb http://ppa.launchpad.net/varlesh-l/papirus-pack/ubuntu bionic main # désactivé pour la mise à niveau vers bionic
# deb-src http://ppa.launchpad.net/varlesh-l/papirus-pack/ubuntu xenial main