SUPPORT WEBGL COPY-PASTE

Runtime/Plugins/platform/webgl/webgl.jslib

 
     UIWidgetsMessageSetObjectName: function (name) {
         UIWidgetsPlugin.getMessageManager().setObjectName(Pointer_stringify(name));
+    },
+    
+    UIWidgetsCopyTextToClipboard: function (text) {
+        var el = document.createElement('input');
+        el.value = Pointer_stringify(text);
+        el.setAttribute('readonly', '');
+        el.style = {
+            position: 'fixed',
+            left: '-9999px',
+        };
+        document.body.appendChild(el);
+        el.select();
+        document.execCommand('copy');
+        document.body.removeChild(el);
     }
 };
 

Runtime/service/clipboard.cs

+using System.Runtime.InteropServices;
 using RSG;
 using UnityEngine;
 
 
     public class UnityGUIClipboard : Clipboard {
         protected override IPromise setClipboardData(ClipboardData data) {
+#if UNITY_WEBGL
+            UIWidgetsCopyTextToClipboard(data.text);
+#else
+#endif
+            
             return Promise.Resolved();
         }
 
         }
+        
+#if UNITY_WEBGL
+        [DllImport ("__Internal")]
+        internal static extern void UIWidgetsCopyTextToClipboard(string text);
+#endif
     }
 }

Samples/UIWidgetSample/HoverRecognizerSample.cs

             return new Scaffold(
                 appBar: new AppBar(
                     title: new Center(
-                        child: new Text("Test Hover Widget")
+                        child: new SelectableText("Test Hover Widget")
                     )
                 ),
                 body: new Card(