Engines like google don’t index 4XX pages because they don’t perform. Subsequently, they’ll ignore any canonical tags pointing to this sort of pages and sometimes turn out indexing the wrong (non-canonical) version of the page. Canonicals ought to generally issue to one of the most authoritative version of a web page. https://bookmarks4seo.com/story18802751/considerations-to-know-about-hreflang-to-non-canonical