Невозможно установить MikTex на Ubuntu 20.04 [дубликат]

Я удаляю MikTex, потому что texstudio не может обновить пакет автоматически. Хочу снова установить. Но вместо этого я получил эту ошибку, когда запустил sudo apt-get update :

Hit:1 http://pl.archive.ubuntu.com/ubuntu focal InRelease
Hit:3 http://pl.archive.ubuntu.com/ubuntu focal-updates InRelease                                                                                                           
Hit:4 http://ppa.launchpad.net/sunderme/texstudio/ubuntu focal InRelease                                                                                                    
Hit:5 http://pl.archive.ubuntu.com/ubuntu focal-backports InRelease                                                                                                         
Hit:6 http://download.opensuse.org/repositories/Ubuntu:/debbuild/Ubuntu_20.04  InRelease                                                                                    
Hit:7 http://deb.playonlinux.com trusty InRelease                                                                                                                           
Hit:8 https://download.docker.com/linux/ubuntu focal InRelease                                                                                                         
Hit:9 http://security.ubuntu.com/ubuntu focal-security InRelease                                                                                
Ign:2 https://ftp.gust.org.pl/TeX/systems/win32/miktex/setup/deb focal InRelease           
Err:11 https://ftp.gust.org.pl/TeX/systems/win32/miktex/setup/deb focal Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses insecure algorithm.  Could not handshake: Error in the certificate verification. [IP: 158.75.62.5 443]
Ign:10 https://cvmrepo.web.cern.ch/cvmrepo/apt focal-prod InRelease
Hit:12 https://cvmrepo.web.cern.ch/cvmrepo/apt focal-prod Release
Reading package lists... Done
E: The repository 'http://miktex.org/download/ubuntu focal Release' no longer has 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 пробовал sudo apt install ca-Certific , но это не удалось. Это тоже не так. не работает Что я могу сделать, если в репозитории / PPA нет файла выпуска? Результат:

~$ sudo ppa-purge ppa:mc3man/trusty-media
Updating packages lists
E: The repository 'http://miktex.org/download/ubuntu focal Release' no longer has a Release file.
Warning:  apt-get update failed for some reason

~$ sudo apt-get update
Hit:1 http://pl.archive.ubuntu.com/ubuntu focal InRelease
Hit:2 http://download.opensuse.org/repositories/Ubuntu:/debbuild/Ubuntu_20.04  InRelease
Hit:3 http://pl.archive.ubuntu.com/ubuntu focal-updates InRelease              
Hit:4 http://ppa.launchpad.net/sunderme/texstudio/ubuntu focal InRelease       
Hit:5 http://deb.playonlinux.com trusty InRelease                              
Hit:7 http://pl.archive.ubuntu.com/ubuntu focal-backports InRelease            
Hit:9 https://download.docker.com/linux/ubuntu focal InRelease                 
Ign:6 https://ftp.gust.org.pl/TeX/systems/win32/miktex/setup/deb focal InRelease
Hit:11 http://security.ubuntu.com/ubuntu focal-security InRelease              
Err:10 https://ftp.gust.org.pl/TeX/systems/win32/miktex/setup/deb focal Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses insecure algorithm.  Could not handshake: Error in the certificate verification. [IP: 158.75.62.5 443]
Ign:8 https://cvmrepo.web.cern.ch/cvmrepo/apt focal-prod InRelease             
Hit:12 https://cvmrepo.web.cern.ch/cvmrepo/apt focal-prod Release
Reading package lists... Done
E: The repository 'http://miktex.org/download/ubuntu focal Release' no longer has 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.

Теперь я не могу установить его снова. Помощь?