https://godotengine.org/
https://o3de.org/
https://defold.com/
https://www.stride3d.net/
https://gdevelop.io/
https://armory3d.org/
https://torque3d.org/engine/
https://flaxengine.com/
https://pragma-engine.com/
https://wickedengine.net/
https://www.adventuregamestudio.co.uk/
https://castle-engine.io/
https://solarus-games.org/
Here's a quick one as I'm on a movie break. I'll make a note to update this in the morning.
Haxe + Haxeflixel : pixel art games
Haxe + Heaps : More general 2d/3d framework with webgl target
Godot : I havent used it personally but I've had a myriad of co-workers tell me how good it is
Monogame/FNA : Open source multi-target C# framework that more or less fits the XNA api. I love this one. Might be really good for C# programmers.
https://godotengine.org/
https://o3de.org/
https://defold.com/
https://www.stride3d.net/
https://gdevelop.io/
https://armory3d.org/
https://torque3d.org/engine/
https://flaxengine.com/
https://pragma-engine.com/
https://wickedengine.net/
https://www.adventuregamestudio.co.uk/
https://castle-engine.io/
https://solarus-games.org/