I've just released the Unity "Adventure Game Engine" on itch: https://tim-rachor.itch.io/age
With it you can create old school point and click adventures without having to worry about coding. On the other hand the engine is quite flexible so it's easy to extend with new features.
(Note: requires a recent version of Unity and some basic Unity knowledge. Manual and tutorial video is available)

Everything free and open source. 😀