Tbh we are a Unity dev team so please don't mind that I had to ask ChatGPT to even remember what other options exist 😅 Here's what it said:

• For Beginners: Start with Construct, Phaser, or GDevelop.
• For 2D Games: Phaser, Construct, Cocos2d-JS, or MelonJS.
• For 3D Games: PlayCanvas, Babylon.js, or Three.js.
• For Customization: Three.js or PixiJS.
• For Open-Source Enthusiasts: Godot or GDevelop.

If you are already working with one of the "bigger" engines, we believe that there should not be a problem. Everything we have done so far with Unity for HTML5 worked perfectly fine. And do know that we won't be looking at the project, just the product how it would work within an iframe.

Have you tried asking on https://forum.godotengine.org/?