Open Source Game Engine Godot
The engine became very popular in recent months. I see madewithgodot hashtag instead of madewithunity in twitter and downloaded in Steam. The language of engine something like python that called gdscript but my opinion scripting is harder . And another interesting thing is node . I still trying to unterstand node
Many new engines have surfaced during these past 3 years. For the best I hope as many are simple and easy to learn.