E: The repository 'https://ppa.launchpadcontent.net/fossfreedom/indicator-sysmonitor/ubuntu jammy 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.
解决办法：
进入到 /etc/apt/sources.list.d 目录下，
打开 fossfreedom-ubuntu-indicator-sysmonitor-jammy.list 文件，
将下面的内容注释掉：
由
deb https://ppa.launchpadcontent.net/fossfreedom/indicator-sysmonitor/ubuntu/ jammy main
变
# deb https://ppa.launchpadcontent.net/fossfreedom/indicator-sysmonitor/ubuntu/ jammy main
