Setup Universal RP
The Universal Render Pipeline (URP) is a prebuilt Scriptable Render Pipeline, made by Unity. URP provides artist-friendly workflows that let you quickly and easily create optimized graphics across a range of platforms, from mobile to high-end consoles and PCs. For more information check this page.
1. Install URP in your RTS Engine Project
In your RTS Engine project, import the Universal RP from the package manager.
Once imported, follow this guide to setup the universal URP in your RTS Engine project. In short, you need to create a URP asset file in the projec tab then assign that URP asset in the Project Settings's Graphics tab. Then upgrade your shaders if they are not URP-compatible by using the Render Pipeline Converter.
2. Configure the RTS Engine Camera Stack
2.1 Configure Main Camera
In a RTS Engine map scene, locate the main camera:
In the Camera component, make sure it has Base as its Render Type:
The main camera should have the Main Camera UI as its child object (responsible for displaying UI elements only on top of the rendering of regular objects in the main camera), select this UI camera and set its Render Type to Overlay and disable the Render Shadows option (because we do not need the UI camera to render shadows) in the Rendering Tab.
Now back to the Main Camera and in the Stack tab, add the Main Camera UI as an overlay.
2.2 Configure Minimap Camera
In the Minimap Camera Controller (find it in the scene's hierarchy attached to GameManager -> Modules -> Minimap, you have two options for rendering the minimap camera: Render Always or Take Snapshot. There are two possible configurations for each rendering type.
2.2.1 Render Always
If you select Render Always for the minimap's camera rendering type, then you can do a similar thing for the Minimap Camera and Minimap Camera UI in terms of having the former as the base rendering camera and adding the UI camera as an overlay.
2.2.2 Take Snapshot
If you select Take Snapshot for the minimap's camera rendering type, then the Minimap Camera will only render the map once and then save what is rendered (output) into a Render Texture then will get disabled. This option is great because it reduces rendering overhead in case the terrain of your map scene remains unchanged and only entities are spawned or despawned which will be visualized by minimap UI icons rendered by a separate camera.
In this case, stacking the UI camera on top of it is not a solution because nothing will be rendered.
The solution here is to leave both Minimap Camera and Minimap UI Camera render types' to Base so no camera stacking. The Minimap (main) Camera will get disabled and only the Minimap UI Camera will continue to render the minimap icons and other UI elements during the game.
2.2.3 Minimap Camera Output
In both of the above cases, make sure that the Minimap Camera and Minimap UI Camera have their Output Texture assigned to the appropriate Render Texture that are rendered by the UI elements of the minimap.