Hello @mandriva2010 Cyril,
Bonjour et bienvenue.
As a ROME user you must know that sudo dnf upgrade/update is not the proper command.
ROME (and Cooker) have to run distro-sync
Second please read this topic and the relevant ones provided with the links.
We suggest to check it every time you are going to update ROME 
This topic in the Italian forum may be interesting to read as well. Use a translator if you need, but looks like simple enough to understand.
Also it may be useful to know your ‘starting point’ before system update:
cat /etc/openmandriva-release
Coming back to the issue you reported please do:
sudo dnf clean all;dnf clean all
But skip this step if already tried to upgrade and the packages are still in dnf cache so you don’t have to download them again.
Then:
sudo dnf remove falkon-kde
sudo dnf --allowerasing -x kdf distro-sync 2>&1|tee rome-dsync.log.txt
Adding “-x kdf” will exclude it from the transaction.
Attach here the file rome-dsync.log.txt if you get any further console error or conflict.
We’ll have to learn what to do as we go.
Feel free to ask more if you have any other question.
Once the users get accustomed with the basic the process will be more and more easy.