How create a mobile/pc or radar disolay hud and interact with its not using scaleform or flash. The example pictures in under the post.
Monitor/CCTV is done by using Render To Texture functionality, more here: Render To Texture Blueprint Toolset | Unreal Engine Documentation
Mobile display would be a combination of the previous technique with overlaying sprites, as described here: Blueprint: Helpful BP Functions - Programming & Scripting - Unreal Engine Forums
The actual implementation can vary wildly depending on your needs but this should give you good pointers.