Unity learning platform is free for three months

Unity Learn
Unity Learn provides award-winning free tutorials, sample projects, and full courses for mastering real-time 3D development skills with Unity Learn to make video games, VR, AR, and more.

Lightbend learning platform is free. They are the creators of Akka.

Lightbend Platform - The Cloud Native Application Platform Built On Akka | @lightbend
Lightbend Platform is the most operationally robust solution for deploying Reactive Microservices, adding the ability to infuse your applications with intelligence based on real-time streaming and Machine Learning (ML).