Manual:$wgSitemapNamespaces

Search: $wgSitemapNamespaces
Array of namespaces identified by their IDs to generate a sitemap or false for all namespaces.
Introduced in version:	1.13.0
Removed in version:	Still in use
Allowed values:	(array) or `false`
Default value:	`false`
Other settings: Alphabetical \| By function

Details

Array of namespace IDs to generate a sitemap for when the maintenance/generateSitemap.php script is run, or false if one is to be generated for all namespaces.

$wgSitemapNamespaces = [
    0,
    2,
    4,
    12
];

Now only sitemap files for the main (0), user (2), project (4) and help (12) namespace will be generated and thus included into the sitemap.