Fennec 65 is not open for new sign-offs. It's either too early or too late to do that. There is a current accepted sign-off, which is used for shipping Fennec 65.
|Jan. 14, 2019
|104 missing, 32 obsolete, (89%)
Bug 1509583 - Migrate region/language names resources to Fluent, part 1.
Enrique Estévez Fernández <firstname.lastname@example.org> rev 15aeb0c939f7
Francesco Lodolo accepted sign-off by Francesco Lodolo on Jan. 14, 2019