所以我收到了这个错误：
E: The repository 'http://ppa.launchpad.net/f-muriana/ubuntu-builder/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.
有人能帮忙吗？哦，我在 ubuntu 20.04
答案1
sudo nano /etc/apt/sources.list
找到这一行。
deb http://ppa.launchpad.net/f-muriana/ubuntu-builder/ubuntu focal Release
注释掉它（用这一行替换那一行）
# deb http://ppa.launchpad.net/f-muriana/ubuntu-builder/ubuntu focal Release
按 ctrl+O 保存文件，然后按 Enter。按 ctrl+x 退出
现在运行
sudo apt-get update