Yes, you must use Mapbox attribution:
https://docs.mapbox.com/help/getting-st … frameworks
The easiest way is to use the attribution prefab from the Mapbox SDK for Unity.

This is more of a legal question than a technical one. When displaying a map using MapBox as tile provider in Online Maps, do we need to provide any MapBox related watermark on screen? When you are using the MapBox for Unity SDK they tell you that you need to add a watermark to the screen.

Cheers,

Jürgen