I am attempting to add a second locale to a site with existing content, much of that content in matrix fields.
Following the documentation for Setting Up a Localized Site, I have defined the locale, enabled all sections for this locale (and the original one), set up the configuration and the index.php files. What I have not yet done is mark any field as translatable.
What I was expecting is that entries in the new locale would be initialized with content from the original locale. And this has happened, except that the matrix fields have not been duplicated, so the entries in the new locale do not have any of that matrix content.
This is very similar to How do I get Matrix elements to copy their content across language Locales?. The answer there is "don't mark matrix fields as translatable", which I haven't done, so not sure why this isn't working for me.