JSitemap supports multiple sitemaps one per each language installed on your Joomla system.
You can create multiple sitemaps one per each language having the related link and submit them to Google Webmasters Tools/Search Console and add them to your robots.txt. When a multilanguage system is installed and enabled on your Joomla website, you will get the multilanguage dropdown to switch between languages and change sitemap links to be submitted as usual.
In the SEO Dashboard the multilanguage dropdown will be available if the multilanguage is enabled on your Joomla website, this allows to format multilanguage links for each sitemap.
If you don't see the multilanguage dropdown it's likely your Joomla website is not really set as a multilanguage one and the Joomla System - Language plugin is not activated. You can force the multilanguage dropdown to be visible in the SEO Dashboard using the parameter below: