As once of the core feature of WordPress 5.5 is the auto sitemaps XML, but if you already have SEO plugins installed, this may cause duplication or conflict with sitemaps that is generated from the SEO plugins. Therefore, is better to disable the sitemaps feature in WordPress 5.5

All you need is just add this line of code snippet in the child theme or plugin Code Snippets

add_filter( 'wp_sitemaps_enabled', '__return_false' );