Hi, I had a quick look ...
You should be able to reproduce this upgrade path by using a throwaway minimal bullseye chroot (e.g. a pbuilder chroot), install mpdscribble there, then install the bookworm version (or a proposed fix) over it.
in bullseye you used ucf to manage the file (to insert username/password), in bookworm you ship it as a conffile.
AND manage it with ucf. That is seriously broken. Andreas
