Please only one problem per thread. For the systemsettings issue, if it is reproducible then you should report it as a bug:
https://wiki.mageia.org/en/How_to_report_a_bug_properlyFor the language setting in your shell, best add the output of
localeIt would also be interesting how you ended up with that setting, as usually it is only set to one language. And yes, this would be a fallback, with english as primary and italian as fallback.
See e.g.
https://www.gnu.org/software/gettext/ma ... E-variableAlthough the language settings by systemsettings can also be manually edited, as they simply end up in a shell script which is sourced by your session, although I don't know where it's located for KDE5 otoh.
Might be in ~/.kde/env/ but I'd have to check.