Ok .. installation of illumian 1.0 was a dive into history in regards to graphic desktop support :)
Manual installation of all xorg/gnome/etc packages via apt-get was required,
and even xdm/gdm/.. was missing in the repos.
However, after symlinking libgcc_s.so to /usr/lib (all gcc stuff is 'only' in their local /usr/gcc* folders)
and installing NVidia's proprietary driver 290.10,
at least I could get our precompiled Solaris binaries to run under twm :)
Guess it's too early for illumian .. so I will check it out at a later time.