软件和更新未显示。从终端 ->
kristina@kristina-desktop:~$ sudo apt install update-manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package update-manager is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'update-manager' has no installation candidate
我想先升级到 Ubuntu 20，然后再升级到 22
答案1
我花了 3 个小时才解决这个问题，我下载了 Bionic.zip 并将 /apt 复制到 /etc .. 然后我就可以做所有的事情了。经过长时间的努力，我的问题以这种方式解决了。