Upgrade Ubuntu 20.04 to 22.04 fails; too many broken packages reported

Question

I was upgrading my initial Ubuntu 18.04 installation to 20.04 without any issues. sudo apt upgrade does not report any outstanding packages. However, trying to upgrade to 22.04 with sudo do-release-upgrade fails:

...
Calculating the changes
Could not determine the upgrade
An unresolvable problem occurred while calculating the upgrade.
This was likely caused by:

Unofficial software packages not provided by Ubuntu

Please use the tool 'ppa-purge' from the ppa-purge
package to remove software from a Launchpad PPA and
try the upgrade again.
If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.
Restoring original system state
Aborting
...

Looking into apt.log with $ cat /var/log/dist-upgrade/apt.log | grep roken reports tons of broken packages (this is just an excerpt):

Starting pkgProblemResolver with broken count: 54
Starting 2 pkgProblemResolver with broken count: 54
Broken libapparmor1:amd64 Breaks on libapparmor-perl:amd64 < 2.13.3-7ubuntu5.1 @ii mK Ib > (< 3.0.3-3)
Broken gnome-settings-daemon:amd64 Breaks on libmutter-6-0:amd64 < 3.36.9-0ubuntu0.20.04.2 @ii mK > (< 3.37)
Broken gnome-shell:amd64 Breaks on gnome-shell-extension-desktop-icons:amd64 < 20.04.0-3~ubuntu20.04.6 @ii mK > (< 21.04)
Broken libgcc1:amd64 Depends on gcc-11-base:amd64 < 11.1.0-1ubuntu1~18.04.1 -> 11.3.0-1ubuntu1~22.04 @ii umU > (= 11.1.0-1ubuntu1~18.04.1)
Broken fuse3:amd64 Breaks on fuse:amd64 < 2.9.9-3 -> 2.9.9-5ubuntu3 @ii umU >
Broken qtbase5-dev:amd64 Breaks on qt5-default:amd64 < 5.12.8+dfsg-0ubuntu2.1 @ii mK Ib > (< 5.15.1+dfsg-2~)
Broken libayatana-appindicator3-1:amd64 Conflicts on libappindicator3-1:amd64 < 12.10.1+20.04.20200408.1-0ubuntu1 -> 12.10.1+20.10.20200706.1-0ubuntu1 @ii umU >
Broken gir1.2-unity-7.0:amd64 Conflicts on gir1.2-unity-5.0:amd64 < 7.1.4+19.04.20190319-0ubuntu3 @ii mK >
Broken usrmerge:amd64 Conflicts on libpng12-0:amd64 < 1.2.54-1ubuntu1.1 @ii mK > (< 1.2.54-4~)
Broken libobjc4:amd64 Depends on libgc1:amd64 < none | 1:8.0.6-1.1build1 @un uH > (>= 1:7.2d)
Broken libnfsidmap1:amd64 Conflicts on libnfsidmap2:amd64 < 0.25-5.1ubuntu1 @ii mK Ib >
Broken libnfsidmap1:amd64 Breaks on libnfsidmap2:amd64 < 0.25-5.1ubuntu1 @ii mK Ib > (< 0.25-7~)
Broken libtss2-esys-3.0.2-0:amd64 Breaks on libtss2-esys0:amd64 < 2.3.2-1ubuntu0.20.04.1 @ii mK > (< 3.0.2-1)
Broken php-common:amd64 Breaks on php7.0-common:amd64 < 7.0.33-0ubuntu0.16.04.16 @ii mK >
Broken qemu-system-x86:amd64 Breaks on qemu-kvm:amd64 < 1:4.2-3ubuntu6.23 @ii mK Ib >
Broken guile-2.2-libs:amd64 Depends on libgc1:amd64 < none | 1:8.0.6-1.1build1 @un uH > (>= 1:7.4.2)
Broken libboost1.74-dev:amd64 Conflicts on libboost1.71-dev:amd64 < 1.71.0-6ubuntu6 @ii mK >
Broken xfce4-helpers:amd64 Breaks on libexo-helpers:amd64 < 0.12.11-1ubuntu1.20.04.1 @ii mK >
Broken libgupnp-av-1.0-3:amd64 Breaks on libgupnp-av-1.0-2:amd64 < 0.12.11-2 @ii mK > (< 0.14)
Broken libobjc-9-dev:amd64 Depends on libobjc4:amd64 < 11.1.0-1ubuntu1~18.04.1 | 12.1.0-2ubuntu1~22.04 @ii umR > (>= 9.5.0-1ubuntu1~22.04)
Broken libobjc-5-dev:amd64 Depends on libobjc4:amd64 < 11.1.0-1ubuntu1~18.04.1 | 12.1.0-2ubuntu1~22.04 @ii umR > (>= 5.5.0-12ubuntu1)
Broken libsepol-dev:amd64 Breaks on libsepol1-dev:amd64 < 3.0-1ubuntu0.1 @ii mK Ib > (< 3.2)
...

What does this messages tell me ? Are there some remainder from Ubuntu 18.04 which were not / couldn't get updated ? How do I resolve that ?

I tried all those suggestions with sudo apt install -f or sudo dpkg --configure -a without success.

I'm stuck and would need some help on how to get out of that to upgrade to 22.04, please. Thanks