I noticed that there is a preinstalled package named ddns-scripts_nsupdate which conflicts with the needed ddns-scripts-nsupdate package (note the subtle difference: _ vs -).
The conflicting file is /usr/lib/ddns/update_nsupdate.sh
This should be corrected (or better yet, put nsupdate back in the base build, since out of the box the rfc2136 dyndns update choice is completely non-functional, with no visual indication of such)