This attribute comes in clutch for pages that function the default Model for users whose language or place doesn’t match any hreflang tags.  If none of these are definitely employed, Google will depend on other indicators like hreflang, interior links, and URL duration to decide on a canonical for yourself https://addons.prestashop.com/it/seo-indicizzazione-naturale/31857-google-rich-snippet-automatico-json-ld-open-graph-seo.html