Launchpad currently recommends translating grub2 in Ubuntu Cosmic.

Template "grub" in Ubuntu Cosmic package "grub2"

Language Status Untranslated Need review Changed Last Edited By
Cherokee 100.00  100.0% untranslated 1380 1380 0 0
Dakota 100.00  100.0% untranslated 1380 1380 0 0
Hawaiian 100.00  100.0% untranslated 1380 1380 0 0
Inuktitut 100.00  100.0% untranslated 1380 1380 0 0
Lakota 100.00  100.0% untranslated 1380 1380 0 0
Ojibwe 100.00  100.0% untranslated 1380 1380 0 0
Spanish 000.00  100.0% translated 0 0 3 3 2018-10-17 20:05:53 UTC 2018-10-17 Miguel Ángel Arruga Vivas
Tlingit 100.00  100.0% untranslated 1380 1380 0 0
Yiddish 100.00  100.0% untranslated 1380 1380 0 0
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Key to this table: “Unchanged” means Translated
and “untranslated” means just that, Untranslated

Other versions of grub2 in Ubuntu