E: The repository 'xxx' is not signed.

在ubuntu上安装了google chrome, 运行时有问题，删除了之后再次运行 sudp apt update 会报错

E: The repository 'http://dl.google.com/linux/chrome/deb stable InRelease' is not signed.

解决方法是：打开Software updater 程序，选择other software, 在列表中去除掉 dl.google.com，即可

参考网页：https://cloudcone.com/docs/article/how-to-fix-the-repository-is-not-signed-error-on-ubuntu-20-04/