Невозможно получить обновления безопасности на Focal

synaptic выдает мне ошибки при попытке обновления, поэтому я попытался запустить sudo apt update в командной строке, но вот результат:

Hit:1 https://download.mono-project.com/repo/ubuntu stable-focal InRelease
Hit:2 https://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu focal InRelease                                                                                  
Hit:3 https://packages.microsoft.com/repos/ms-teams stable InRelease                                                                                                 
Hit:4 https://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu focal-updates InRelease                                                    
Hit:5 https://www.mirrorservice.org/sites/archive.ubuntu.com/ubuntu focal-backports InRelease                                                  
Err:6 https://security.ubuntu.com/ubuntu focal-security InRelease                                                        
  Could not connect to security.ubuntu.com:443 (91.189.88.142). - connect (111: Connection refused) Could not connect to security.ubuntu.com:443 (91.189.88.152). - connect (111: Connection refused) Could not connect to security.ubuntu.com:443 (91.189.91.38). - connect (111: Connection refused) Could not connect to security.ubuntu.com:443 (91.189.91.39). - connect (111: Connection refused)
Hit:7 https://repo.skype.com/deb stable InRelease                                                
Ign:8 https://dl.google.com/linux/earth/deb stable InRelease
Hit:9 https://dl.google.com/linux/chrome/deb stable InRelease
Hit:10 https://dl.google.com/linux/earth/deb stable Release
Reading package lists... Done
Building dependency tree       
Reading state information... Done
All packages are up-to-date.
N: Skipping acquisition of configured file 'main/binary-i386/Packages', as repository 'https://download.mono-project.com/repo/ubuntu stable-focal InRelease' doesn't support architecture 'i386'
N: Skipping acquisition of configured file 'main/binary-i386/Packages', as repository 'https://dl.google.com/linux/chrome/deb stable InRelease' doesn't support architecture 'i386'
N: Skipping acquisition of configured file 'main/binary-i386/Packages', as repository 'https://dl.google.com/linux/earth/deb stable InRelease' doesn't support architecture 'i386'
W: Failed to fetch https://security.ubuntu.com/ubuntu/dists/focal-security/InRelease  Could not connect to security.ubuntu.com:443 (91.189.88.142). - connect (111: Connection refused) Could not connect to security.ubuntu.com:443 (91.189.88.152). - connect (111: Connection refused) Could not connect to security.ubuntu.com:443 (91.189.91.38). - connect (111: Connection refused) Could not connect to security.ubuntu.com:443 (91.189.91.39). - connect (111: Connection refused)
W: Some index files failed to download. They have been ignored, or old ones used instead.

Я заметил, что у некоторых людей была похожая проблема, которая была решена отключением IPv6, но это было после того, как я это сделал (раньше были ошибки и в адресах IPv6). Я проверил журналы брандмауэра и DNS, и запросы на security.ubuntu.com, похоже, ничем не блокируются.