https://manpages.ubuntu.com/manpages/resolute/man3/SDL_FingerID.3type.html
Ubuntu Manpage: SDL_FingerID - A unique ID for a single finger on a touch device.
A unique ID for a single finger on a touch device.
https://docs.unity3d.com/2020.2/Documentation/ScriptReference/Touch-fingerId.html
Unity - Scripting API: Touch.fingerId
scripting apiunitytouch