I believe, the problem is been caused by wrong informations in /var/lib/dpkg/info from the native installed debian/stable, where I qant to build it.
ALL *.postinst files are pointing to trixie and not to bookworm (although, the installed packages are all from bookworm). So, with the view on the official release of trixie in a short time, I will not bother you any more with my issue. For the interested: I will next try to correct the files in /var/lib/dpkg/ info, then download a live-file of debian stable and try to build within that environment. And when trixie is out, the problems will be resolved anyway. So, thank you all for your help and your efforts to solve my little issue! I mark it as solved, please do not waste any more time on this! Best regards Hans
