Maybe root into cd/ and list all the repositories installed? /etc/apt/sources.list And just remove the ones listed perhaps. What do you think Banana?
You mean "remove the listed repositories *but Trisquel's*", right? That is the "text-editing" equivalent to what I suggested at the end of https://trisquel.info/forum/warning-following-packages-cannot-be-authenticated#comment-79268 (using the, probably less intimidating, "Software & Updates" window): You can finally remove the repositories from the menu Configuration/Software source (tab "Other software").
But removing a repository does not remove the packages that were installed from it, hence the previous steps in my post.
