由于各种原因，19.04 停产后，我不得不继续使用一段时间。现在我想升级到 20.04。我尝试了多种方法，例如此处描述的步骤顺序： https://www.reddit.com/r/Lubuntu/comments/g3390k/1904_the_repository_standard_repo_no_longer_has_a/
简而言之，这意味着：
sudo sed -i 's/disco/focal/g' /etc/apt/sources.list
sudo apt update && sudo apt full-upgrade
我收到的错误信息似乎在互联网上重现，如下所示：
E: The repository 'http://ppa.launchpad.net/deadsnakes/ppa/ubuntu disco 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.
N: Skipping acquire of configured file 'universe/binary-i386/Packages' as repository 'http://miktex.org/download/ubuntu xenial InRelease' doesn't support architecture 'i386'
E: The repository 'http://ppa.launchpad.net/maarten-baert/simplescreenrecorder/ubuntu disco 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.
我想现在已经过去很久了，肯定有人在某个地方找到了解决办法，不是吗？有人知道该怎么办吗？
谢谢！