所以我最近安装了 Focal Fossa，现在我无法使用任何 sftp/ftp 配置文件。更奇怪的是，我可以使用终端在那些我曾经使用文件浏览器的服务器上执行 scp/ssh 之类的命令。
我尝试遵循另一篇文章中的一些内容无法连接到 Nautilus 中的服务器，但无济于事。
软件和更新部分甚至没有他们提到的字段；更不用说任何复选框了。
以下是该命令的打印输出sudo apt install gvfs-backends：
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 resolve the situation:
The following packages have unmet dependencies:
gvfs-backends : Depends: libsmbclient (>= 2:4.10.0+dfsg) but 2:4.7.6+dfsg~ubuntu-0ubuntu2.21 is to be installed
E: Unable to correct problems, you have held broken packages.
我尝试跟踪未满足的依赖关系链，但感觉就像试图杀死九头蛇一样。更深的下一层只会出现越来越多的问题。任何帮助都将不胜感激。
编辑 #1：尝试将我的 sources.list 文件恢复为默认设置。没有变化。 我如何恢复默认存储库
编辑#2：被要求提供以下命令输出。
为了sudo apt-get update
Hit:1 http://archive.canonical.com/ubuntu focal InRelease
Hit:2 http://archive.ubuntu.com/ubuntu focal InRelease
Hit:3 http://dl.google.com/linux/chrome/deb stable InRelease
Ign:4 http://extras.ubuntu.com/ubuntu focal InRelease
Err:5 http://extras.ubuntu.com/ubuntu focal Release
404 Not Found [IP: 91.189.88.91 80]
Hit:6 http://archive.ubuntu.com/ubuntu focal-security InRelease
Hit:7 http://archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:8 http://archive.ubuntu.com/ubuntu focal-proposed InRelease
Hit:9 http://archive.ubuntu.com/ubuntu focal-backports InRelease
Reading package lists... Done
E: The repository 'http://extras.ubuntu.com/ubuntu focal Release' does not have 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.
为了sudo apt-cache policy gvfs-backends libsmbclient
gvfs-backends:
Installed: (none)
Candidate: 1.44.1-1ubuntu1
Version table:
1.44.1-1ubuntu1 500
500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
libsmbclient:
Installed: 2:4.7.6+dfsg~ubuntu-0ubuntu2.21
Candidate: 2:4.11.6+dfsg-0ubuntu1.6
Version table:
2:4.11.6+dfsg-0ubuntu1.6 500
500 http://archive.ubuntu.com/ubuntu focal-security/main amd64 Packages
500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
2:4.11.6+dfsg-0ubuntu1 500
500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
*** 2:4.7.6+dfsg~ubuntu-0ubuntu2.21 100
100 /var/lib/dpkg/status
编辑＃3：
输出sudo apt-get upgrade && sudo apt-get dist-upgrade
Hit:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:2 http://archive.ubuntu.com/ubuntu focal InRelease
Hit:3 http://archive.canonical.com/ubuntu focal InRelease
Hit:4 http://archive.ubuntu.com/ubuntu focal-security InRelease
Hit:5 http://archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:6 http://archive.ubuntu.com/ubuntu focal-proposed InRelease
Hit:7 http://archive.ubuntu.com/ubuntu focal-backports InRelease
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
linux-headers-generic-hwe-18.04 linux-image-generic-hwe-18.04
Use 'sudo apt autoremove' to remove them.
The following packages have been kept back:
gdb gir1.2-peas-1.0 libpeas-1.0-0 libsmbclient libwbclient0 samba-libs
0 upgraded, 0 newly installed, 0 to remove and 6 not upgraded.
Pastebin：grep 命令的输出