In a fully up-to-date bionic VM with French as the default language/locale, I enabled bionic-proposed and installed the thunderbird update (1:78.8.1+build1-0ubuntu0.18.04.1), and I verified that the UI is fully localized in French, including menus, preferences, etc…
In a fully up-to-date bionic VM with French as the default language/locale, I enabled bionic-proposed and installed the thunderbird update (1:78.8. 1+build1- 0ubuntu0. 18.04.1) , and I verified that the UI is fully localized in French, including menus, preferences, etc…