Reconfiguration of xserver-xorg package fails on 12.04 LTS with Raring HWE installed

Question

I am attempting to remove fglrx (proprietary AMD/ATI drivers) and install the radeon open source driver.

I am following the steps here:

RadeonDriver - Community Ubuntu Documentation
https://help.ubuntu.com/community/RadeonDriver

X/Troubleshooting/VideoDriverDetection - Ubuntu Wiki
https://wiki.ubuntu.com/X/Troubleshooting/VideoDriverDetection#Problem:_Need_to_purge_-fglrx

In particular, I just executed these three steps:

sudo apt-get remove --purge xorg-driver-fglrx fglrx*
sudo apt-get install --reinstall xserver-xorg-lts-raring libgl1-mesa-glx-lts-raring libgbm1-lts-raring
sudo dpkg-reconfigure xserver-xorg

The output of the last command was:

/usr/sbin/dpkg-reconfigure: xserver-xorg is broken or not fully installed

What should I do next?

I'm running Kubuntu 12.04 with the lts-raring hardware enablement stack installed.

Solution

The problem is that when you have installed the LTS hardware enablement stack, you can no longer use the regular xserver-xorg and related packages. This command will certainly fail:

sudo dpkg-reconfigure xserver-xorg

However, a command similar to this should work:

sudo dpkg-reconfigure xserver-xorg-lts-raring

However, it can be more complicated than that, and in my case it certainly was!

In order to solve my problem, I had to reappropriate the solution from here: https://askubuntu.com/a/344625/36661

Note that the solution is proposed for a completely unrelated question! However, I want to point out that those same steps can also solve this question. (Mods, please don't confuse the fact that I reappropriated an answer for the questions being duplicates -- the questions are unrelated!)

The solution is in response to this unrelated question:

12.04 - Experiencing major issues on graphic displays - Ask Ubuntu
Experiencing major issues on graphic displays

Comments

[Glutanimate]

I think this Q&A should be reopened. This is not a duplicate. The cause for the problems OP is experiencing is a completely different one than in the linked Q&A. While the solution in the other Q&A might work in OP's case, it's overcomplicated and dangerous compared to the answer given below.

[Braiam]

What is the output of sudo apt-get check?

[TiloBunt]

sudo dpkg-reconfigure xserver-xorg-lts-saucy for 13.10 stack