update engine

com.unity.uiwidgets/Runtime/engine/UIWidgetsPanel.cs

         }
 
         void Input_OnEnable() {
-#if !UNITY_EDITOR && (UNITY_IOS || UNITY_ANDROID)
-            Input.RawTouchEvent += ProcessRawTouch;
-#endif
+            UnityEngine.UIWidgets.InitUIWidgets.init();
+            UnityEngine.UIWidgets.RawTouchEvent += ProcessRawTouch;
             _inputMode = Input.mousePresent ? UIWidgetsInputMode.Mouse : UIWidgetsInputMode.Touch;
         }
 
             Canceled = 4
         }
 
-        void ProcessRawTouch(Input.RawTouchEventParam param) {
+        void ProcessRawTouch(UnityEngine.UIWidgets.RawTouchEventParam param) {
             var position = _getPointerPosition(new Vector2(param.x, param.y));
             var pointerId = -1 - param.pointerId;
             switch ((TouchPhase)param.phase) {
         }
 
         void Input_OnDisable() {
-#if !UNITY_EDITOR && (UNITY_IOS || UNITY_ANDROID)
-            Input.RawTouchEvent -= ProcessRawTouch;
-#endif
+            UnityEngine.UIWidgets.RawTouchEvent -= ProcessRawTouch;
         }
 
         void Input_Update() {

com.unity.uiwidgets/package.json

 	"unity": "2019.4",
 	"description": "UIWidgets allows you to build beautiful cross-platform apps through Unity",
 	"dependencies": {
+		"com.unity.modules.uiwidgets": "1.0.0"
 	}
 }