One a particular site we have multiple languages but we do not detect them via any of the admin/config/regional/language/configure options.
As a consequence, XML Sitemap still allows adding and populating a sitemap per language, but - because the language prefix is not in the URL - all of these sitemaps have identical URL: http://example.com/sitemap.xml
I see two solutions
- either adding the defined language prefix in the name, e.g. http://example.com/sitemap_en.xml, etc. (preferred)
- or allowing to edit not just the language but also the file name per sitemap
Happy to provide a patch if the maintainer(s) think it's a good approach (I see the first solution as the better one).