Ubuntu 19.04: problemas ao executar o apt update

Estou tentando instalar o phpmyadmin no Ubuntu 19.04 e me meti no seguinte problema. Alguém pode me ajudar com isso?

Minha pergunta é diferente de todas as perguntas que alguns caras estão se referindo. Não sei ao certo onde eles encontraram semelhança, mas olhando para a pergunta deles, minha pergunta é certamente diferente.

sudo apt update
Hit:1 https://download.docker.com/linux/ubuntu bionic InRelease
Ign:2 http://dl.google.com/linux/chrome/deb stable InRelease                   
Hit:3 https://repo.skype.com/deb stable InRelease                              
Hit:4 http://security.ubuntu.com/ubuntu disco-security InRelease               
Hit:5 http://repo.mysql.com/apt/ubuntu disco InRelease                         
Hit:6 http://dl.google.com/linux/chrome/deb stable Release                     
Hit:8 http://linux.teamviewer.com/deb stable InRelease                         
Hit:9 http://archive.ubuntu.com/ubuntu disco InRelease                         
Hit:10 http://packages.microsoft.com/repos/vscode stable InRelease             
Err:11 http://in.mirrors.ustc.edu.cn/ubuntu disco InRelease                    
  Connection failed [IP: 202.141.176.110 80]
Err:12 http://in.mirrors.ustc.edu.cn/ubuntu disco-updates InRelease
  Connection failed [IP: 202.141.176.110 80]
Err:13 http://in.mirrors.ustc.edu.cn/ubuntu disco-backports InRelease
  Connection failed [IP: 202.141.176.110 80]
Reading package lists... Done
Building dependency tree       
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://in.mirrors.ustc.edu.cn/ubuntu/dists/disco/InRelease  Connection failed [IP: 202.141.176.110 80]
W: Failed to fetch http://in.mirrors.ustc.edu.cn/ubuntu/dists/disco-updates/InRelease  Connection failed [IP: 202.141.176.110 80]
W: Failed to fetch http://in.mirrors.ustc.edu.cn/ubuntu/dists/disco-backports/InRelease  Connection failed [IP: 202.141.176.110 80]
W: Some index files failed to download. They have been ignored, or old ones used instead.

Esta é a saída do comando sudo apt-get update

Hit:1 http://linux.teamviewer.com/deb stable InRelease
Hit:2 http://repo.mysql.com/apt/ubuntu disco InRelease                         
Hit:3 https://repo.skype.com/deb stable InRelease                              
Hit:4 http://packages.microsoft.com/repos/vscode stable InRelease              
Get:5 http://security.ubuntu.com/ubuntu disco-security InRelease [97.5 kB]     
Hit:6 http://ppa.launchpad.net/ondrej/php/ubuntu disco InRelease               
Hit:7 https://download.docker.com/linux/ubuntu bionic InRelease                
Ign:8 http://dl.google.com/linux/chrome/deb stable InRelease                   
Hit:9 http://archive.ubuntu.com/ubuntu disco InRelease                         
Hit:10 http://dl.google.com/linux/chrome/deb stable Release         
Err:12 http://in.mirrors.ustc.edu.cn/ubuntu disco InRelease                    
  Connection failed [IP: 202.141.176.110 80]
Err:13 http://in.mirrors.ustc.edu.cn/ubuntu disco-updates InRelease
  Connection failed [IP: 202.141.176.110 80]
Err:14 http://in.mirrors.ustc.edu.cn/ubuntu disco-backports InRelease
  Connection failed [IP: 202.141.176.110 80]
Fetched 97.5 kB in 16s (6,182 B/s)                        
Reading package lists... Done
W: Failed to fetch http://in.mirrors.ustc.edu.cn/ubuntu/dists/disco/InRelease  Connection failed [IP: 202.141.176.110 80]
W: Failed to fetch http://in.mirrors.ustc.edu.cn/ubuntu/dists/disco-updates/InRelease  Connection failed [IP: 202.141.176.110 80]
W: Failed to fetch http://in.mirrors.ustc.edu.cn/ubuntu/dists/disco-backports/InRelease  Connection failed [IP: 202.141.176.110 80]
W: Some index files failed to download. They have been ignored, or old ones used instead.

Eu descobri que eu sources.listtinha alguns links de origem que não existiam mais. Eles foram adicionados durante minha tentativa de instalar outro software. Então, sempre que eu estava tentando executar um sistema de atualização, não era possível buscar os pacotes necessários.

Consegui resolver o problema usando a resposta desta postagem substituindo a lista de fontes

Agora, meu problema foi corrigido e eu consigo instalar o outro software.