System updater

When I start that graphic tool, I have a pop up with a French title and English text inside asking "Include latest updates from the internet?", plus some more English text, there are 3 buttons, 1 is in French (for settings) and 2 are in English (check for updates and ask me later). Do people using another language than English and French have similar mix of English and their preferred language?

In the settings, in the "Trisquel software" tab, near "download from", there is a a drop down list with "Main server" and "Other", if I select "Other" I have a list of countries and within, a list of mirrors. However, in the "Other software tab", I have a number of lines for archive.trisquel.info.

Then, when I look at /etc/apt/sources.list, I have archive.trisquel.org, which is neither the mirror I selected in the GUI tool nor the archive.trisquel.info that I saw in the GUI tool.

So I am wondering, does the GUI tool use something else than /etc/apt/sources.list? If yes, how to see what it uses? At the moment, I have many failures when I run "sudo apt update" so I am not sure it works, but the GUI tool does not say anything and I don't know whether it is because it uses a mirror that works or because it does not work but the tool says nothing. Is there a way to see some kind of terminal output when running the graphical tool?

Besides, I am not sure where to find the official list of mirrors.