Gregory's ServerDefinitely agree, there are lots of great libre game engine options to consider. Godot is probably the most polished I know of, but if you're looking for others, here is a list of some projects to check out (in no particular order):
O3DE - o3de.org
Wicked Engine - wickedengine.net
Three.js - threejs.org
Fyrox Engine - fyrox.rs
@bevy - bevyengine.org
LÖVE - love2d.org
@lovr - lovr.org
Ogre Engine - ogre3d.org
@gdevelop - gdevelop.io
Armory - armory3d.org
@xenko - stride3d.net