If you are new to GNU/Linux it is easy to be confused about the difference
between the operating system and the desktop environment, because Window$ and
macOS don't offer multiple desktop environments. You can think of the DE as
the graphical interface over the underlying OS.
LXDE (the default DE in Trisquel Mini) and Gnome Classic (the default in
Trisquel) are both included in the Trisquel repository, along with XFCE, KDE
Plasma, Gnome 3, Enlightenment, and many others. You can install and use
whichever one you want, regardless of which one is installed by default.
If you want to try Trisquel's default DE, as some here have suggested, there
is no need to install regular Trisquel. Within Trisquel Mini, you can install
the DE with
$ sudo apt install trisquel trisquel-recommended
To try it out, log out, click on the little icon near your name, select the
DE you want to use, and log in.