Comment 1 for bug 1783129

I don't think is the intention, so thanks for the bug.

Curtin should be updating the default source.list in the image with any configuration changes. In this case, we're updating the URI to use a mirror if one is selected.

Can you collect two things?

1) During the install, switch to the debugging screen and capture the /etc/apt/sources.list of the installer environment

2) After install capture the /etc/apt/sources.list file

Please attach both.