WordPress 5.5 add core XML sitemap functionnality, but there is no user interface to disable it or to mange contents within theses files.
Disable WordPress XML sitemaps simply deactivate all WordPress XML sitemaps and redirect them to your home URL, preventing 404 page generation for Google and other Search Engines.
This SEO enhancement is already included in our SEOKEY plugin. Not only do we deactivate WordPress native XML sitemaps (which are not optimized), but SEOKEY replaces them with much more powerful sitemaps (better crawl, not any harmful content).
More information here about it : Core XML Sitemap Guide (French)