Encontrei uma solução alternativa sem ter que jogar com preseeds.
Localize no iso squashfs: etc / lib / ubiquity / localechooser / localechooser
# Always support English (unless preseeded otherwise), so that we
# get English language packs etc.
if [ "$english" ]; then
db_set $tpl_supportedlocales "$new"
else
db_set $tpl_supportedlocales "${new:+$new, }en_US.UTF-8"
fi
}
Alterei as seguintes linhas:
# Always support English (unless preseeded otherwise), so that we
# get English language packs etc.
if [ "$english" ]; then
db_set $tpl_supportedlocales "$new"
else
# MODIFIED, original line is commented below
# db_set $tpl_supportedlocales "${new:+$new, }en_US.UTF-8"
# Either or not the language is english, keep only the selected language.
db_set $tpl_supportedlocales "$new"
fi
}
Funciona muito bem.