Some comment on how that works

config.yaml

@@ -17,7 +17,13 @@ markup:
 languages:
   da:
     title: data.coop
-    weight: 1
+    weight: 1    
+    # First Hugo looks in your post front matter for an images value (images: [""])
+    # Then Hugo searchs for image page resources with feature, cover or thumbnail in their name. These are images files under a directory that matches the post (e.g. content\posts\first-post)
+    # If not images are found, Hugo looks for images (images: [""]) in your site config
+    # If no image if found, then an image-less Twitter summary card is used instead of summary_large_image
+    # https://digitaldrummerj.me/hugo-preview-when-sharing-twitter/
+    images: ["/static/img/some_card_preview_large_en.png"]
     LanguageName: Dansk
     menu:
       nav:
@@ -36,6 +42,7 @@ languages:
   en:
     title: data.coop
     weight: 2
+    images: ["/static/img/some_card_preview_large_da.png"]
     LanguageName: English
     menu:
       nav:

themes/datacoop2020/layouts/partials/head.html

@@ -17,6 +17,9 @@
         <meta name="msapplication-TileColor" content="#4b3aba">
         <meta name="theme-color" content="#4b3aba">
 
+        {{ template "_internal/twitter_cards.html" . }}
+        {{ template "_internal/opengraph.html" . }}
+
         {{ $style := resources.Get "static/css/style.scss" | resources.ToCSS | resources.Minify | resources.Fingerprint "sha512" }}
         <link rel="stylesheet" href="{{ $style.RelPermalink }}" integrity="{{ $style.Data.Integrity }}">