Comment 3 for bug 1584685

I can't reproduce this issue here; trying to install ubuntu-server and preseeding apt-setup/local0/repository="http://ppa.launchpad.net/cyphermox/ppa/ubuntu zesty main".

The preseeded repository is indeed showing in sources.list and is written correctly.

If you can still reproduce this bug, please include both the exact preseed used, along with the full contents of /etc/apt/sources.list at the end of the install so we can see what happens.