Languages: bizarre behavior

I have done a new KDE Neon’s installation from an official DVD, with de 6.5 version; currently, it is in the 6.5.3 version.

I want to use Basque language (Euskara). If I choose Basque in the system settings, I have applications in two languages, Basque and English.

For example, Konsole although I have chosen Basque language.

I thought it would be because of an incomplete translations. However, if I choose Spanish in System Settings (Español de España), I can see applications in Basque without problem, but, of course, the system’s language is Spanish.

Any solution for having all the system and applications in basque?

Thanks

When I choose Basque, these are my languages files:

/home/jon/.config/plasma-localerc:

[Formats]
LANG=eu_ES.UTF-8@euro
LC_ADDRESS=eu_ES.UTF-8@euro
LC_MEASUREMENT=eu_ES.UTF-8@euro
LC_MONETARY=eu_ES.UTF-8@euro
LC_NAME=eu_ES.UTF-8@euro
LC_NUMERIC=eu_ES.UTF-8@euro
LC_PAPER=eu_ES.UTF-8@euro
LC_TELEPHONE=eu_ES.UTF-8@euro
LC_TIME=eu_ES.UTF-8@euro

[Translations]
LANGUAGE=eu:es

And my locale:

jon@xxxxxxxx:~$ locale
LANG=eu_ES.UTF-8@euro
LANGUAGE=eu:es:eu:es
LC_CTYPE=“eu_ES.UTF-8”
LC_NUMERIC=“eu_ES.UTF-8”
LC_TIME=“eu_ES.UTF-8”
LC_COLLATE=“eu_ES.UTF-8”
LC_MONETARY=“eu_ES.UTF-8”
LC_MESSAGES=“eu_ES.UTF-8”
LC_PAPER=“eu_ES.UTF-8”
LC_NAME=“eu_ES.UTF-8”
LC_ADDRESS=“eu_ES.UTF-8”
LC_TELEPHONE=“eu_ES.UTF-8”
LC_MEASUREMENT=“eu_ES.UTF-8”
LC_IDENTIFICATION=“eu_ES.UTF-8”
LC_ALL=eu_ES.UTF-8

When I choose Spanish:

/home/jon/.config/plasma-localerc:

[Formats]
LANG=es_ES.UTF-8
LC_ADDRESS=es_ES.UTF-8
LC_MEASUREMENT=es_ES.UTF-8
LC_MONETARY=es_ES.UTF-8
LC_NAME=es_ES.UTF-8
LC_NUMERIC=es_ES.UTF-8
LC_PAPER=es_ES.UTF-8
LC_TELEPHONE=es_ES.UTF-8
LC_TIME=es_ES.UTF-8

[Translations]
LANGUAGE=es:eu

And my locale:

jon@jon-aspirer3131t:~$ locale
LANG=es_ES.UTF-8
LANGUAGE=eu:es:es:eu
LC_CTYPE=“es_ES.UTF-8”
LC_NUMERIC=es_ES.UTF-8
LC_TIME=es_ES.UTF-8
LC_COLLATE=“es_ES.UTF-8”
LC_MONETARY=es_ES.UTF-8
LC_MESSAGES=“es_ES.UTF-8”
LC_PAPER=es_ES.UTF-8
LC_NAME=es_ES.UTF-8
LC_ADDRESS=es_ES.UTF-8
LC_TELEPHONE=es_ES.UTF-8
LC_MEASUREMENT=es_ES.UTF-8
LC_IDENTIFICATION=C.UTF-8
LC_ALL=