The dpkg -> xz-utils downgrade problem has a suggestion that suggests itself.
1) Downgrade dpkg's dependency to the last known good. It doesn't matter how old so long as it can read the file formats. I understand this is likely to be 5.4.1. 2) Statically link all the decompressor libraries into dpkg. Yes this means gzip, bzip2, zstd, and xz's libraries. Today's compile and link time optimizers are pretty good; it should be able to drop all references to the compression side pretty much by itself. This would generally be a pretty good change of its own as it makes the minimal system easier to understand and the net-install CD smaller. Then you're free to do what you need to do for all the other dependencies of xz-utils.
