[SOLVED] Distribution upgrade Stretch to Buster fails

[Roy Terhaar]

Software
XBian version:1.0 (knockout) (kernel: Linux 4.19.75+)
XBMC/Kodi version:118.4-Git:20191006-104b22a-dirty
Overclock settings:default

Hardware
Device type and model (e.g. Raspberry Pi Model A/B 256/512 MB, CuBox-i i4Pro, ...):RPI 3b+
Power supply rating:Original power supply adapter
SD card size and make/type:32Gb
Network (Ethernet or wireless):Kodi using Ethernet; wireless adapter active too on different network
Connected devices (TV, USB, network storage, ...):Philips TV, External USB harddisks Seagate and Seagate Backup Plusi

Log files
-

Problem description:
Trying to upgrade the distribution of Stretch to Buster via the Kodi/XBian gui fails displaying on the screen somewhere halfway the installation process:
Errors were encountered while processing:
util-linux
mount
initscripts
sub-process /usr/bin/dpkg returned an error code (1)

I have already tried the standard things found on the internet regarding the dpkg error, but none seems to work solving the problem.

I have checked contents of sources.list:
deb http://http.debian.net/debian stretch main non-free
And xbian.list:
deb http://apt.xbian.org/ stable main rpi2-stretch armv7l-stretch
Looks ok I guess...and during upgrade process 'stretch' gets replaced by 'buster', so that seems to be ok.

I have tried to reinstall the three problem packages:
sudo apt-get install --reinstall util-linux (this one shows a lot of warnings)
sudo apt-get install --reinstall mount (no warnings here)
sudo apt-get install --reinstall initscripts (this one shows a lot of warnings too)
The warnings refer to missing symbolic links in /etc/rcS.d
I am not sure if this can be the cause of the upgrade problem, but it is a possibility right?
This is part of the warnings shown on screen:
sudo apt-get install --reinstall util-linu x
[sudo] password for xbian:
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 0 B/917 kB of archives.
After this operation, 0 B of additional disk space will be used.
Create a snapshot of '/run/xbian-storage/root/@' in '/run/xbian-storage/root/@bt rfs-auto-snap_apt-run-2019-11-03-1824'
Delete subvolume (no-commit): '/run/xbian-storage/root/@last_good_known'
Create a snapshot of '/run/xbian-storage/root/@btrfs-auto-snap_apt-run-2019-11-0 3-1824' in '/run/xbian-storage/root/@last_good_known'
Delete subvolume (no-commit): '/run/xbian-storage/root/@btrfs-auto-snap_apt-run- 2019-11-03-1743'
@btrfs-auto-snap_apt-run-2019-11-03-1824, 1 created snapshots, 0 sent snapshots, 1 destroyed snapshots, 0 created filesystems, 0 warnings.
(Reading database ... 40271 files and directories currently installed.)
Preparing to unpack .../util-linux_2.29.2-1+deb9u1_armhf.deb ...
Unpacking util-linux (2.29.2-1+deb9u1) over (2.29.2-1+deb9u1) ...
Setting up util-linux (2.29.2-1+deb9u1) ...
initctl: Unknown job: K01nfs-common
insserv: warning: script 'K01nfs-common' missing LSB tags and overrides
initctl: Unknown job: K01nfs-common
initctl: Unknown job: S02dbus
insserv: warning: script 'S02dbus' missing LSB tags and overrides
initctl: Unknown job: S02dbus
initctl: Unknown job: S02dbus
initctl: Unknown job: S02dbus
initctl: Unknown job: K01nfs-common
initctl: Unknown job: S04nfs-common
initctl: Unknown job: S04checkroot-bootclean.sh
insserv: warning: script 'S04checkroot-bootclean.sh' missing LSB tags and overrides
initctl: Unknown job: S04mountnfs-bootclean.sh
insserv: warning: script 'S04mountnfs-bootclean.sh' missing LSB tags and overrides
initctl: Unknown job: S04mountdevsubfs
insserv: warning: script 'S04mountdevsubfs' missing LSB tags and overrides
initctl: Unknown job: S04mountkernfs
insserv: warning: script 'S04mountkernfs' missing LSB tags and overrides
initctl: Unknown job: S04mtab

Right now I am kinda stuck resolving this problem.

Anybody any suggestions?