Launchpad currently recommends translating gfxboot-theme-ubuntu in Ubuntu Cosmic.

Template "bootloader" in Ubuntu Cosmic package "gfxboot-theme-ubuntu"

Language Status Untranslated Need review Changed Last Edited By
Cherokee 100.00  100.0% untranslated 90 90 14 14 0 2013-06-17 19:39:40 UTC 2013-06-17
Dakota 100.00  100.0% untranslated 90 90 0 0
Hawaiian 100.00  100.0% untranslated 90 90 0 0 2011-07-31 18:55:40 UTC 2011-07-31
Inuktitut 070.00  30.0% translated  70.0% untranslated 63 63 0 0 2013-04-29 15:38:13 UTC 2013-04-29 Thomassie Mangiok
Lakota 100.00  100.0% untranslated 90 90 0 0
Ojibwe 100.00  100.0% untranslated 90 90 17 17 0 2009-11-17 21:49:21 UTC 2009-11-17
Spanish 000.00  100.0% translated 0 0 14 14 2018-10-14 01:24:42 UTC 2018-10-14 Paco Molinero
Tlingit 100.00  100.0% untranslated 90 90 0 0
Yiddish 095.56  4.44444444444% translated  95.5555555556% untranslated 86 86 0 0 2009-10-14 14:29:32 UTC 2009-10-14 Janis96
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Key to this table: “Unchanged” means Translated
and “untranslated” means just that, Untranslated

Other versions of gfxboot-theme-ubuntu in Ubuntu