When designing interactions in Unity and Unreal, it's possible to change which fingers interact/collide with objects in the scene.
In Unreal - by default the ring and little fingers have collisions turned off to prevent accidentally triggering items in the scene. If you wish to use these fingers to interact, this article will guide you through the process.
In Unity - collision is active on all fingers by default. If you wish to modify which fingers can begin an interaction, check out the Interaction Hand. It can be used to specify which fingertips cause a hover on objects. Learn more here.