As I was writing in this post:
On Windows, all applications include all dependencies and you end up
downloading/installing/running the same libraries tens of times, the
well-know abusive RAM consumption mainly comes from that.
All the dependencies of apt-offline must already be installed in your system.
I therefore assume you are complaining about the dependencies of
apt-offline-gui. Indeed, it is a Qt application and Qt is not included in
Trisquel's default installation. What about using the apt-offline command to
install apt-offline-gui?