Why can I not uninstall this package?

[Tim Woodall <debianuser@woodall.me.uk>]

I have an old eeepc that I've just upgraded to bullseye. It was getting
very limited on diskspace so I've been going through removing packages
that I no longer require or in some cases, appear to be very old
versions that have been left lying around.

I've now got things under control. However I've hit the following weird
case that I don't understand:

eeepc:/var/lib/dpkg/info# apt-get remove libjbig0
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libreoffice-base-core : Depends: libreoffice-core-nogui (= 1:7.0.4-4+deb11u1) but it is not going to be installed or
                                  libreoffice-core (= 1:7.0.4-4+deb11u1) but it is not going to be installed
 python3-uno : Depends: libreoffice-core-nogui (= 1:7.0.4-4+deb11u1) but it is not going to be installed or
                        libreoffice-core (= 1:7.0.4-4+deb11u1) but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be
caused by held packages.


This makes no sense to me. apt rdepends libjbig0 lists a handful of
packages none of which I have installed.

libreoffice-core is installed (and the version that is being asked for)

If I remove python3-uno then that problem goes away (until I reinstall
it). I don't want to uninstall libreoffice-base-core.

I haven't yet tried using dpkg to remove the package.

How can I debug what has gone wrong here?

This is a very old debian install that has been updated over the years.
The oldest files I still see in /var/lib/dpkg/info are:
-rw-r--r-- 1 root root     249 Mar 25  2010 libvolume-id0.list
-rw-r--r-- 1 root root     290 Aug 25  2009 libvolume-id0.md5sums
-rwxr-xr-x 1 root root     135 Aug 25  2009 libvolume-id0.postinst
-rwxr-xr-x 1 root root     132 Aug 25  2009 libvolume-id0.postrm
-rw-r--r-- 1 root root    2179 Aug 25  2009 libvolume-id0.symbols
-rw-r--r-- 1 root root      29 Apr 19  2009 libvolume-id0.shlibs

Tim.