https://godotengine.org I only took it for a quick test run a few weeks ago when they released the latest version. I would say that it is quite similar to Unity, if you have unity experience then you will get quickly up to speed with godot. I liked it, I am quite certain that I will try and finish my current Unity project and after that I'll switch to using godot instead. It it is free and a small download so no reasons to not give it a try!