Google uses both schema.org markup and og:image meta tag for thumbnails in Google Search and Discover

Google clarified this within its Google image best practices and Google Discover documentation.

Google Clarifies How It Picks Thumbnails For Search, Discover

Google updated its Image SEO and Discover documentation to explain how schema markup and the og:image meta tag influence ...
Search Engine Land

Google updates image SEO best practices to say use the same image URL for same image across your pages

Google updated its Google image SEO best practices help document to recommend that you use the same image file name URL for the same image, even if you place that same image on different pages on your ...