apt-get无法连接Ubuntu主软件源求助

我最近执行apt-get update命令更新软件源的时候遇到了麻烦，直接弹出了错误提示：

Err:1 http://ke.archive.ubuntu.com/ubuntu focal InRelease
  Cannot initiate the connection to ke.archive.ubuntu.com:80 (2c0f:fe40:8001:10::1). - connect (101: Network is unreachable) 
  Could not connect to ke.archive.ubuntu.com:80 (197.155.77.1), connection timed out

之后我尝试了一个解决思路，修改了/etc/apt/sources.list文件，把里面的ke.archive.ubuntu.com替换成了官方主源地址archive.ubuntu.com，但问题依然存在，新的错误提示如下：

Err:1 http://archive.ubuntu.com/ubuntu focal InRelease
  Cannot initiate the connection to archive.ubuntu.com:80 (2620:2d:4000:1::16). - connect (101: Network is unreachable)
  Cannot initiate the connection to archive.ubuntu.com:80 (2620:2d:4002:1::102). - connect (101: Network is unreachable)
  Cannot initiate the connection to archive.ubuntu.com:80 (2620:2d:4...

备注：内容来源于stack exchange，提问作者contemplator