// Exclude posts marked with exclude_from_blog meta from the main blog feed
add_action("pre_get_posts", function($query) {
    if (!is_admin() && $query->is_main_query() && ($query->is_home() || $query->is_feed())) {
        $query->set("meta_query", array(
            "relation" => "OR",
            array(
                "key"     => "exclude_from_blog",
                "compare" => "NOT EXISTS",
            ),
            array(
                "key"     => "exclude_from_blog",
                "value"   => "1",
                "compare" => "!=",
            ),
        ));
    }
});
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://couplesonthemove.com/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://couplesonthemove.com/wp-sitemap-posts-post-1.xml</loc></sitemap><sitemap><loc>https://couplesonthemove.com/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://couplesonthemove.com/wp-sitemap-taxonomies-category-1.xml</loc></sitemap><sitemap><loc>https://couplesonthemove.com/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>