nrfutil is only supported by Python 2 at the moment so I suggest that you uninstall it from Python 3. That should resolve the dependency conflict for now.
I didn't know nrfutil was included in the dependency list in nrf/scripts/requirements.txt. That will cause nrfutil to be installed as a Python 3 package instead of a Python 2 package. So we should remove nrfutil from the "requirements.txt" list in NCS until we get the Python 3 support in place. I will report this internally.
