Replaced EditorUtility.GetMiniThumbnails() to AssetPreview.GetMiniThumbnail()
Replaced EditorUtility.ReplacePrefab() to PrefabUtility.ReplacePrefab()
Replaced EditorUtility.ResetGameObjectToPrefabState() to PrefabUtility.ResetToPrefabState();
By the way, I’m not sure just replace ‘ReplacePrefabOptions.UseLastUploadedPrefabRoot’ option to ‘ReplacePrefabOptions.Default’ which is passed to PrefabUtility.ReplacePrefab() method.
ReplacePrefabOptions.UseLastUploadedPrefabRoot seems to be deprecated.