Well if yo move a head a little it actully quite easy to figure how to do it in UE4
It’s image aligned to 2 axis (X, Y) of world, scrolls depending on player position, you can make material that takes player position as parameter and scroll image based on it, but thats just one way of doing it. Ofcorse you need to do image somehow, you can make screen of top view of map and photoshop it in some fancy way.
2)Make sphere trace that searches for objects of interest or you can hold things in arrays, read positions of objects and only use 2 axis (X, Y) and substract agains X, Y of player position, so you got distance vectors which ten you can apply in HUD on top of minimap. Feather objects are displayed like a compass based on angle, you need to calculate angle of distance vector and place icon on HUD in right angle from player