Downgrading is trivial: apt-get install xserver-xorg-lts-precise libgl1-mesa-{dri,glx}:i386
This is unsupported for newer hardware, because they're not tested with the older linux/xserver, but in your case it would work. It seems some interaction with multiarch is making it fail. Multiarch was already failing to switch correctly, causing the 32-bits libs to be uninstalled. If I install enough 32-bits applications I can make it uninstall kubuntu-desktop too.
But the failure the other way around is easier to test:
Notice that ia32-libs gets removed by installing xserver-xorg-lts-quantal. However if I install ia32-libs afterwards it works, because that case was fixed in #1130419:
pbuilder-dist precise amd64 login
apt-get install --install-recommends xserver-xorg-lts-quantal
apt-get install --install-recommends ia32-libs
It's still easy to make the resolver die completely, too:
Downgrading is trivial: apt-get install xserver- xorg-lts- precise libgl1- mesa-{dri, glx}:i386
This is unsupported for newer hardware, because they're not tested with the older linux/xserver, but in your case it would work. It seems some interaction with multiarch is making it fail. Multiarch was already failing to switch correctly, causing the 32-bits libs to be uninstalled. If I install enough 32-bits applications I can make it uninstall kubuntu-desktop too.
But the failure the other way around is easier to test:
pbuilder-dist precise amd64 login recommends ia32-libs xserver- xorg-lts- precise recommends xserver- xorg-lts- quantal
apt-get install --install-
apt-get install --install-
Notice that ia32-libs gets removed by installing xserver- xorg-lts- quantal. However if I install ia32-libs afterwards it works, because that case was fixed in #1130419: recommends xserver- xorg-lts- quantal recommends ia32-libs
pbuilder-dist precise amd64 login
apt-get install --install-
apt-get install --install-
It's still easy to make the resolver die completely, too:
pbuilder-dist precise amd64 login recommends xserver- xorg-lts- precise recommends xserver- xorg-lts- quantal ia32-libs
apt-get install --install-
apt-get install --install-
if you add libgl1- mesa-{glx, dri}-lts- quantal: i386 to the last line, it will find the correct solution.