Notes: I had only a samll problem in the new system: gnome-terminal didn't load. On bugzilla.redhat searching for gnome-terminal I found a solution that solved the "locale" issue, installing "langpacks-it".
went downloading, at some time the system notified free disk space at minumum (~1,1G). So during the process I deleted some files obtaining about 8 G free.
Neverthless, at the end of the command many recent files was signed not installable because of insufficient space.
"sudo dnf system-upgrade reboot"
and system rebooted twice but without upgrade. Re-launching previous dnf s*-u* download command resulted in skipping pkgs as already downloaded (but incomplete).
So after manual remove of /var/cache/PackageKit/27 and repeating the process, this time all went fine.
Check free disk space, please! (Perhaps in GUI this doesn't happen!?) Thank you all!