mp1985

thanks for your reply.

as you suggested, I disabled the caching system and then I tried to add the filter, but without luck.

add_filter( 'the_seo_framework_sitemap_additional_urls', function( $custom_urls = []) {

    $custom_urls[ $url ] = [ 
        'https://example.com/somepage' => [ 'lastmod' => '2021-12-16 10:58' ],
    ];

	return $custom_urls;
} );

What I am missing or doing wrong?

moreover, do you know if it is possible with this filter instead of including just one page, to include directly also a second external sitemap (and keeping the default sitemap that your plugin creates)?

thanks a lot for the plugin