这是我得到的结果 sudo apt-get update
W: The repository 'http://ppa.launchpad.net/t-tujikawa/ppa/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/t-tujikawa/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
我该如何解决这个问题？
sascha@sascha-HP-250-G7-Notebook-PC:~$ sudo apt update
[sudo] Passwort für sascha:
OK:1 http://dl.google.com/linux/chrome/deb stable InRelease
OK:2 http://de.archive.ubuntu.com/ubuntu focal InRelease
Holen:3 http://de.archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
OK:4 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal InRelease
Holen:5 http://de.archive.ubuntu.com/ubuntu focal-backports InRelease [101 kB]
Holen:6 http://de.archive.ubuntu.com/ubuntu focal-security InRelease [109 kB]
Ign:7 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main amd64 DEP-11 Metadata
Ign:8 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main DEP-11 48x48 Icons
Ign:9 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main DEP-11 64x64 Icons
Ign:10 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main DEP-11 64x64@2 Icons
Ign:11 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main amd64 c-n-f Metadata
Ign:7 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main amd64 DEP-11 Metadata
Ign:8 http://ppa.launchpad.net/gezakovacs/ppa/ubuntu focal/main DEP-11 48x48 Icons …如何通知 Launchpad PPA 格式错误？
语境：
我正在尝试安装https://launchpad.net/~feignint/+archive/ubuntu/dosbox-staging中列出的当前稳定版本的 dossbox-staging
在 Ubuntu 20.04 上，apt-get install dosbox-staging安装版本。0.76 而不是 0.78.1
看看我是不是要疯了。。。
apt-cache policy dosbox-staging
dosbox-staging：已安装：（无）候选：0.76.0-1+ubuntu20.04
版本表：0.76.0-1+ubuntu20.04 500 500 http://ppa.launchpad.net/feignint/dosbox-staging/ubuntu focus/main amd64 软件包
这表明 Ubuntu 使用的是“正确的”PPA，而不是 Ubuntu 默认安装所使用的存储库。
不幸的是，Launchpad 不允许我登录（尽管凭据正确），因此我无法联系发布者“feignint”，他可能是 SE 用户@FeignInt
这个问题不是骗人的。我在这里收到了我想要的答案：https : //unix.stackexchange.com/a/411530/3285
以前，当我只是尝试更新时会收到此错误。我相信这个问题与VLC PPA有关，它在 Ubuntu 上一直是彻头彻尾的垃圾。rm为了清除*vlc*包，我实际上必须删除受包控制的文件。现在，我删除了那个文件，我可以相对轻松地删除 vlc 包。我想这会让我回到开始，我可以再次尝试安装，但是当我这样做时，我收到了这个错误，
sudo apt-get install vlc
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to …