Hi @crowlkats @jdejutter, other than the Unity for Desktop SDK, you can in principal use the Tobii Stream Engine API with the Tobii Eye Tracker 5 which offers low-level access to all of the data streams.
Certainly, for games, you should ideally use the Unity for Desktop SDK.
To enquire about availability, please make a request @ https://developer.tobii.com/software-downloads/