I was able to solve the issue. As I wrote in the recent article, it had to do with the M$ C++ Redistributable packages. Either a conflict or something was missing or a configuration problem. Using sxstrace is not of much help. If you are not familiar with this stuff, you will only get a bunch of information, but you would not know, what to do with it. And I doubt, that someone with no deep knowledge of M$ programming will find the cause in the trace file.

What I did was to delete/ uninstall ALL C++ redistributable packages before running setup.

( CAUTION : This can/ will cause issues with other applications ).

I then ran the Domino 9.0.0 setup. At the very end of the setup process, the installer installs the correct vcredist packages.

I guess that my first attempt to fix the issue by reinstalling Domino failed, because the files where already in place and were not reinstalled during installation