Problèmes de dépendances non satisfaites lors de l'installation de python2.7 - Ubuntu 18.04

J'ai récemment réinstallé Ubuntu 18.04 et je souhaite maintenant installer python2.7 pour diverses autres dépendances, mais je n'y parviens pas. Je lance sudo apt install python y sudo apt install python-minimal Les deux ont des erreurs très similaires :

Python:

Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 python : PreDepends: python-minimal (= 2.7.15~rc1-1) but it is not going to be installed
          Depends: python2.7 (>= 2.7.15~rc1-1~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Python-minimal :

Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 python-minimal : Depends: python2.7-minimal (>= 2.7.15~rc1-1~) but it is not going to be installed
                  Recommends: python but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

L'installation de python2.7-minimal produit alors des résultats :

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 python2.7-minimal : Depends: libpython2.7-minimal (= 2.7.15-4ubuntu4~18.04.1) but 2.7.15-4ubuntu4~18.04.2 is to be installed
                     Recommends: python2.7 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

L'installation de python2.7 rencontre exactement la même erreur que précédemment, et libpython2.7 est déjà installée, puisque apt-cache policy libpython2.7 retours :

libpython2.7:
  Installed: 2.7.15-4ubuntu4~18.04.2
  Candidate: 2.7.15-4ubuntu4~18.04.2
  Version table:
 *** 2.7.15-4ubuntu4~18.04.2 100
        100 /var/lib/dpkg/status
     2.7.15-4ubuntu4~18.04.1 500
        500 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic-updates/main amd64 Packages
        500 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic-security/main amd64 Packages
     2.7.15~rc1-1 500
        500 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic/main amd64 Packages

Oui, j'ai couru sudo apt update y upgrade et je cherche des réponses depuis plusieurs jours sans succès. Toute aide serait grandement appréciée, car je pense que l'impossibilité d'installer python2.7 pourrait être liée au fait qu'Ubuntu ne peut pas reconnaître les ports matériels (tels que HDMI) et ne peut pas modifier la luminosité.

Informations sur le matériel : Nom du produit : Acer Aspire A715-72G Processeur : Intel(R) Core(TM) i5-8300H CPU @ 2.30GHz Carte graphique supplémentaire : GP107M (GeForce GTX 1050 Mobile)

Je suis très novice en matière d'Ubuntu, et d'Unix en général, donc j'espère que c'est une erreur de débutant et que c'est facilement réparable. C'est la première question que je pose, donc s'il y a quelque chose que je dois ajouter, dites-le moi.

Toute aide serait grandement appréciée, merci beaucoup !

EDIT : Ajouter la sortie de sudo apt update

Hit:1 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic InRelease
Hit:2 http://ppa.launchpad.net/apandada1/brightness-controller/ubuntu bionic InRelease              
Hit:3 http://archive.canonical.com/ubuntu bionic InRelease                                          
Hit:4 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic-updates InRelease                    
Ign:5 http://ppa.launchpad.net/fkrull/deadsnakes/ubuntu bionic InRelease                            
Hit:6 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic-backports InRelease                  
Hit:7 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu bionic InRelease                         
Hit:8 http://ftp.ticklers.org/archive.ubuntu.org/ubuntu bionic-security InRelease                   
Err:9 http://ppa.launchpad.net/fkrull/deadsnakes/ubuntu bionic Release                              
  404  Not Found [IP: 91.189.95.83 80]
Reading package lists... Done                                                 
E: The repository 'http://ppa.launchpad.net/fkrull/deadsnakes/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.