相关疑难解决方法(0)

最近我在旧机器上安装了旧版本的 Ubuntu。每当我尝试安装任何软件时，都会收到一条错误消息，说找不到它：

$ sudo apt-get install vlc
Reading package lists... Done               
Building dependency tree       
Reading state information... Done    
E: Couldn't find package vlc

我正在使用 Ubuntu 20.04.3 LTS。我已经遇到错误 2 天了，即由于以下错误，我无法在系统上更新或升级或执行软件包安装：

Hit:1 http://packages.microsoft.com/repos/code stable InRelease                                                                   
Hit:2 http://archive.canonical.com/ubuntu focal InRelease                                                                         
Hit:3 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu focal InRelease                                                              
Hit:4 http://dl.google.com/linux/chrome/deb stable InRelease                                                                      
Ign:5 http://old-releases.ubuntu.com/ubuntu focal InRelease                                                                       
Ign:6 http://old-releases.ubuntu.com/ubuntu focal-updates InRelease                                                               
Hit:7 http://ppa.launchpad.net/kicad/kicad-5.1-releases/ubuntu focal InRelease                                                    
Hit:8 https://deb.opera.com/opera-stable stable InRelease                                                                         
Hit:9 https://packages.microsoft.com/repos/vscode stable InRelease                                                                
Ign:10 http://old-releases.ubuntu.com/ubuntu focal-backports InRelease                                                            
Ign:11 http://ppa.launchpad.net/team-gcc-arm-embedded/ppa/ubuntu focal InRelease                                           
Ign:12 http://old-releases.ubuntu.com/ubuntu focal-security InRelease                                                      
Err:14 http://old-releases.ubuntu.com/ubuntu focal Release                                                                        
  404  Not Found [IP: 91.189.88.247 80]
Err:15 http://ppa.launchpad.net/team-gcc-arm-embedded/ppa/ubuntu focal Release                                                    
  404  Not Found [IP: 91.189.95.85 80]
Err:16 http://old-releases.ubuntu.com/ubuntu focal-updates Release                                                           
  404  Not …

需要有关这些错误的帮助，我正在从 Raspberry Pi Imager 运行 Ubuntu 版本 (21.10)。

Reading package lists... Done
E: The repository 'http://ports.ubuntu.com/ubuntu-ports impish 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.
E: The repository 'http://ports.ubuntu.com/ubuntu-ports impish-updates 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: …