See https://www.drupal.org/project/drupal/issues/2313309 🐛 Admin toolbar and contextual links should always be rendered in the admin language (if set) Needs work
The patch in #44 there fixes the admin language for the core toolbar menu. Since this module extends the core functionality, there should also be the case when this module is enabled.
Right now, if I apply that patch and enable the admin_toolbar module, I don't see the selected admin language code (English) on a Spanish node for instance.
Postponed
2.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
The patch from #8 is for Drupal 11, see Change record:
New language.admin_language_render service →
There seems to be some activity around this in related core issue.
The patches still seem to apply.
The issue summary would need to be updated.