Обновление sudo apt-get не работает

Я использую Ubuntu 18.04, и когда я пробую команду apt-get update, я получаю:

Hit:1 https://repo.skype.com/deb stable InRelease
Hit:2 http://ppa.launchpad.net/jonathonf/mate-1.22/ubuntu bionic InRelease                                                       
Get:3 http://security.ubuntu.com/ubuntu bionic-security InRelease [88,7 kB]                                                      
Get:4 http://linux.dropbox.com/ubuntu bionic InRelease                                                                                            
Err:4 http://linux.dropbox.com/ubuntu bionic InRelease                                                                                             
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:5 http://dl.google.com/linux/chrome/deb stable InRelease                                                                                       
Err:5 http://dl.google.com/linux/chrome/deb stable InRelease                                                                     
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:6 http://es.archive.ubuntu.com/ubuntu bionic InRelease                                                                   
Err:6 http://es.archive.ubuntu.com/ubuntu bionic InRelease               
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Ign:7 http://ppa.launchpad.net/ubuntu-mate-dev/ppa/ubuntu bionic InRelease
Get:8 http://es.archive.ubuntu.com/ubuntu bionic-updates InRelease       
Err:8 http://es.archive.ubuntu.com/ubuntu bionic-updates InRelease       
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:9 http://es.archive.ubuntu.com/ubuntu bionic-backports InRelease 
Err:9 http://es.archive.ubuntu.com/ubuntu bionic-backports InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Ign:10 http://ppa.launchpad.net/ubuntu-mate-dev/trusty-mate/ubuntu bionic InRelease
Err:11 http://ppa.launchpad.net/ubuntu-mate-dev/ppa/ubuntu bionic Release
  404  Not Found [IP: 91.189.95.83 80]
Err:12 http://ppa.launchpad.net/ubuntu-mate-dev/trusty-mate/ubuntu bionic Release
  404  Not Found [IP: 91.189.95.83 80]
Reading package lists... Done
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://linux.dropbox.com/ubuntu bionic InRelease' is not signed.
E: Failed to fetch http://linux.dropbox.com/ubuntu/dists/bionic/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://dl.google.com/linux/chrome/deb stable InRelease' is not signed.
E: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://es.archive.ubuntu.com/ubuntu bionic InRelease' is not signed.
E: Failed to fetch http://es.archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://es.archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://es.archive.ubuntu.com/ubuntu bionic-updates InRelease' is not signed.
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.
E: Failed to fetch http://es.archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://es.archive.ubuntu.com/ubuntu bionic-backports InRelease' is not signed.
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.
E: The repository 'http://ppa.launchpad.net/ubuntu-mate-dev/ppa/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.
E: The repository 'http://ppa.launchpad.net/ubuntu-mate-dev/trusty-mate/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.

Я понятия не имею, что происходит. Что не так?

Редактировать: есть похожий вопрос, но проблема заключалась в подключении колледжа ОП. Я получаю эту ошибку в разных настройках, поэтому я не думаю, что это проблема