This morning, I stopped waiting.
On my KDE laptop, d-u ran two times. First time:
Calculating upgrade... Done
The following packages will be REMOVED:
kpartsplugin libnepomuk4 libnepomukquery4a libnepomukutils4 plasma-widget-adjustableclock
The following NEW packages will be installed:
linux-headers-4.17.11-towo.1-siduction-amd64 linux-image-4.17.11-towo.1-siduction-amd64
The following packages will be upgraded:
bind9-host binutils binutils-common binutils-x86-64-linux-gnu bsdutils cpp-6 cpp-8 cryptsetup-bin ...
.
.
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248 upgraded, 2 newly installed, 5 to remove and 0 not upgraded.
Need to get 317 MB of archives.
Apt-listbugs still shows a warning on util-linux, but I think it is a different issue than two days ago. So I proceeded with the d-u.
Then a reboot.
Second d-u:
Calculating upgrade... Done
The following packages were automatically installed and are no longer required:
linux-headers-4.17.8-towo.2-siduction-amd64 linux-image-4.17.8-towo.2-siduction-amd64
Use 'apt autoremove' to remove them.
The following packages have been kept back:
cpp-8 g++-8 gcc-8 gcc-8-base libasan5 libatomic1 libcc1-0 libgcc-8-dev libgcc1 libgfortran5
libgomp1 libitm1 liblsan0 libmpx2 libquadmath0 libtsan0 libubsan1 login
The following packages will be upgraded:
akonadi-backend-mysql akonadi-server libkf5akonadi-data libkf5akonadiagentbase5
libkf5akonadicore5abi1 libkf5akonadiprivate5abi1 libkf5akonadiwidgets5abi1
7 upgraded, 0 newly installed, 0 to remove and 18 not upgraded.
Need to get 2,390 kB of archives.
After this operation, 197 kB of additional disk space will be used.
Do you want to continue? [Y/n]
I tested "kdesu konsole" and it works correctly. In a user konsole terminal I tested "su" and it works correctly.
I looked for nepomuk packages and there is only one left:
root@hp-350g:/# apt-cache policy nepomuk*
nepomuk-core-data:
Installed: 4:4.14.3-siduction1
Candidate: 4:4.14.3-siduction1
Version table:
*** 4:4.14.3-siduction1 100
100 /var/lib/dpkg/status
I don't know whether that one is needed any more, or not, so I will leave it until those who know better than me (or apt) says it is not needed.
If there is anything different about my system or my desktop settings, I can't find it by working with it. Probably the Qt 5.11 documentation tells what is changed.
So for me, the waiting is over. Your mileage may vary, of course.