How about this?
$ sudo apt-get autoremove
$ sudo apt-get update
$ sudo apt-get install --reinstall trisquel
(do that connected to the Internet)
"trisquel" is a "metapackage" for the default Trisquel desktop edition; it
depends on many packages so when you (re)install it, it installs every
package needed for its "edition" -- "triskel" brings the default KDE
installation; "trisquel-mini", a lightweight desktop environment.
This is about the packages usually needed, for avoiding the stucking in
"battery mode", which appears to be related with lacking GDM. I don't know
about the KMS issue; as lembas suggested, you could install a newer
linux-libre version and see what happens.
Besides the http://jxself.org/linux-libre/ repository, there's a Linux-libre
PPA ("personal packaging archive") available at
https://launchpad.net/~linux-libre/+archive/ppa with Ubuntu-specific
versions. The instructions for using it are in the "PPA Description":
ADDING THIS PPA TO YOUR SYSTEM:
-------------------------------
sudo add-apt-repository ppa:linux-libre/ppa
INSTALLING LINUX-LIBRE:
-----------------------
sudo apt-get update
sudo apt-get install linux-libre
sudo apt-get dist-upgrade
