This is a paid asset, but now you can download Dynamic Split Screen Free.
Detail this asset from Unity Store: Original Link
Dynamic Split Screen v1.1 (Latest version)
Dynamic Split Screen provides a quick way to prototype 2 player split screen project without caring about rendering.
Supported modes are 2D and 3D top-down view (with camera looking from an angle).
Cameras positions are updated dynamically based on relative player positions, if they are close enough, they will be rendered on single screen.
Features:
– 2D and 3D top-down view support
– custom split line support
– dynamic split screen rotation
– support for changing player screen size and split angle
– ability to change camera distance / ortho size
And all of this works with minimal effort, custom setup takes just 2 clicks and 1 line of code. Sample scenes and documentation are available as part of the package too.