当我尝试在软件更新程序中将 Ubuntu 18.04 更新到 20.04 时，它显示“获取已完成”，然后冻结，几分钟后关闭。
在终端模式下，它基本上做同样的事情：
chas@chas-pc:~$ sudo do-release-upgrade
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,340 kB]
Fetched 1,342 kB in 0s (0 B/s)
authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'
extracting 'focal.tar.gz'
Reading cache
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Get:1 http://ro-mirrors.evowise.com/ubuntu bionic InRelease [242 kB]
Hit http://ro-mirrors.evowise.com/ubuntu bionic-updates InRelease
Hit http://dl.google.com/linux/chrome/deb stable InRelease
Hit http://ro-mirrors.evowise.com/ubuntu bionic-backports InRelease
Hit http://ro-mirrors.evowise.com/ubuntu bionic-security InRelease
Hit http://ppa.launchpad.net/alexlarsson/flatpak/ubuntu bionic InRelease
Ign http://repo.vivaldi.com/stable/deb stable InRelease
Hit http://repo.vivaldi.com/stable/deb stable Release
Hit http://ppa.launchpad.net/dhor/myway/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/eugenesan/ppa/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/inkscape.dev/stable/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/libreoffice/libreoffice-7-0/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/libreoffice/ppa/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/openjdk-r/ppa/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/otto-kesselgulasch/gimp/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/rednotebook/stable/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/savoury1/digikam/ubuntu bionic InRelease
Hit http://ppa.launchpad.net/savoury1/ffmpeg4/ubuntu bionic InRelease
Fetched 242 kB in 0s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
Restoring original system state
Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
chas@chas-pc:~$
我已重复此操作很多次，使用了在互联网上能找到的每一种方法，但结果都是一样的。
有人知道哪里出了问题吗？