Leapp inplace upgrade from RHEL8 to 9 fails for foreman

Problem:
Leapp in place upgrade for foreman/smartproxy fails. Attempting to upgrade from RHEL8 to RHEL9.

Expected outcome:
Leapp upgrade is working

Foreman and Proxy versions:
3.12.0 / katello 4.14.0
Foreman and Proxy plugin versions:

Distribution and version:
RHEL8

Other relevant data:
Following procedure described here:
https://docs.theforeman.org/3.12/Upgrading_Project/index-katello.html#upgrading-foreman-or-smart-proxy-in-place-using-leapp_upgrading-connected

Preupgrade check is working after providing the gpg keys like
cp /var/lib/leapp/el9userspace/etc/pki/rpm-gpg/RPM-GPG-KEY-candlepin /etc/leapp/repos.d/system_upgrade/common/files/rpm-gpg/9

However the real upgrade still fails with some package conflicts.

Stderr: warning: Found bdb_ro Packages database while attempting sqlite backend: using bdb_ro backend.
            warning: Found bdb_ro Packages database while attempting sqlite backend: using bdb_ro backend.
            Warning: Package marked by Leapp to upgrade not found in repositories metadata: gpg-pubkey leapp leapp-upgrade-el8toel9 python3-leapp
            warning: Found bdb_ro Packages database while attempting sqlite backend: using bdb_ro backend.
            warning: Found bdb_ro Packages database while attempting sqlite backend: using bdb_ro backend.
            warning: Found bdb_ro Packages database while attempting sqlite backend: using bdb_ro backend.
     warning: Found bdb_ro Packages database while attempting sqlite backend: using bdb_ro backend.
            Error: Transaction test error:
              file /usr/lib/python3.9/site-packages/__pycache__/six.cpython-39.opt-1.pyc from install of python3-six-1.15.0-9.el9.noarch conflicts with file from package python39-six-1.16.0-2.el8.noarch
              file /usr/lib/python3.9/site-packages/__pycache__/six.cpython-39.pyc from install of python3-six-1.15.0-9.el9.noarch conflicts with file from package python39-six-1.16.0-2.el8.noarch
              file /usr/lib/python3.9/site-packages/six.py from install of python3-six-1.15.0-9.el9.noarch conflicts with file from package python39-six-1.16.0-2.el8.noarch
              file /usr/lib/python3.9/site-packages/iniparse/__pycache__/__init__.cpython-39.opt-1.pyc from install of python3-iniparse-0.4-45.el9.noarch conflicts with file from package python39-iniparse-0.4-35.el8.noarch
              file /usr/lib/python3.9/site-packages/iniparse/__pycache__/__init__.cpython-39.pyc from install of python3-iniparse-0.4-45.el9.noarch conflicts with file from package python39-iniparse-0.4-35.el8.noarch

Whole log at https://paste.mozilla.org/JDzzifhA#L5
Any hints in which direction I should check further or is that possibly an issue in the online foreman leapp repos?

Found solution in Using leapp to upgrade from Rocky 8.10 to Rocky 9 - #16 by dgoodfsa

Python 3.9 was used by Pulp in the past, but isn’t anymore. It should be safe to uninstall it via dnf autoremove or dnf remove python39 .

dnf autoremove did uninstall python39 with some other unneeded packages. Afterwards the upgrade did work.