files.labs.ie
From labs.ie
https://files.labs.ie is an open directory served by nginx. currently it's set to mirror the apt-repo for Ubuntu focal 20.04.
here's an example sources.list that you can use for your ubuntu server:
deb [arch=amd64] https://files.labs.ie/ubuntu focal main restricted universe multiverse deb [arch=amd64] https://files.labs.ie/ubuntu focal-security main restricted universe multiverse deb [arch=amd64] https://files.labs.ie/ubuntu focal-updates main restricted universe multiverse deb [arch=amd64] https://files.labs.ie/ubuntu focal-backports main restricted universe multiverse
this mirror gets updated every hour from the official ubuntu mirrors.