Using a dictionary library for i18n, also shows how to use i18n with navigation plugin.

_includes/layouts/base.njk

@@ -30,7 +30,7 @@
       {#- Read more about `eleventy-navigation` at https://www.11ty.dev/docs/plugins/navigation/ #}
       <ul class="nav">
       {%- for entry in collections.all | eleventyNavigation %}
-        <li class="nav-item{% if entry.url == page.url %} nav-item-active{% endif %}"><a href="{{ entry.url | url }}">{{ entry.title }}</a></li>
+        <li class="nav-item{% if entry.url == page.url %} nav-item-active{% endif %}"><a href="{{ entry.url | url }}">{{ entry.title | i18n }}</a></li>
       {%- endfor %}
       </ul>
     </header>