Launchpad currently recommends translating gtk+3.0 in Ubuntu Bionic.

Template "gtk-3.0" in Ubuntu Bionic package "gtk+3.0"

Language Status Untranslated Need review Changed Last Edited By
Cherokee 100.00  100.0% untranslated 1372 1372 0 0
Dakota 100.00  100.0% untranslated 1372 1372 0 0
Hawaiian 100.00  100.0% untranslated 1372 1372 0 0
Inuktitut 100.00  100.0% untranslated 1372 1372 0 0
Lakota 100.00  100.0% untranslated 1372 1372 0 0
Ojibwe 100.00  100.0% untranslated 1372 1372 0 0
Spanish 000.00  100.0% translated 0 0 20 20 2018-04-19 16:32:25 UTC 2018-04-19 Daniel Mustieles
Tlingit 100.00  100.0% untranslated 1372 1372 0 0
Yiddish 097.30  2.69679300292% translated  97.3032069971% untranslated 1335 1335 0 0 2018-04-19 16:46:38 UTC 2018-04-19 Raphael Finkel
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Template "gtk-3.0-properties" in Ubuntu Bionic package "gtk+3.0"

Language Status Untranslated Need review Changed Last Edited By
Cherokee 100.00  100.0% untranslated 2229 2229 0 0
Dakota 100.00  100.0% untranslated 2229 2229 0 0
Hawaiian 100.00  100.0% untranslated 2229 2229 0 0
Inuktitut 100.00  100.0% untranslated 2229 2229 0 0
Lakota 100.00  100.0% untranslated 2229 2229 0 0
Ojibwe 100.00  100.0% untranslated 2229 2229 0 0
Spanish 000.00  100.0% translated 0 0 28 28 2018-04-19 16:59:51 UTC 2018-04-19 Daniel Mustieles
Tlingit 100.00  100.0% untranslated 2229 2229 0 0
Yiddish 070.61  29.3853746074% translated  70.6146253926% untranslated 1574 1574 0 0 2018-04-19 17:09:03 UTC 2018-04-19 Raphael Finkel
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Key to this table: “Unchanged” means Translated
and “untranslated” means just that, Untranslated

Other versions of gtk+3.0 in Ubuntu