XML sitemaps in core, and the plugin you may not need

5.5 generates sitemaps at /wp-sitemap.xml, which covers most of what an SEO plugin was installed for on a simple site.

// remove a post type from it
add_filter( 'wp_sitemaps_post_types', function ( $types ) {
    unset( $types['attachment'], $types['case_study'] );

    return $types;
} );

// off entirely, when a plugin is already doing it
add_filter( 'wp_sitemaps_enabled', '__return_false' );

Two sitemaps is worse than one: search engines see conflicting sets and the plugin’s and core’s disagree about what is indexable. Turning one off is the first thing to do after any upgrade on a site with an SEO plugin, and most of them now do it themselves. The core version has no priority or change-frequency fields, which is correct — search engines have ignored both for years.