Hello, my background is in UE/Godot/Unity. I've never used lua before. I just have two questions. 

1. Which of these engines have the best UI libraries/UI development components?

For example in Godot, it's really easy for me to set up good looking UIs with boxcontainers and the theming system. Is there anything similar in these engines?

2. Do any of these have anything similar to Godots signal system?

I don't like setting up boilerplate code for observer patterns and other design patterns in game engines. With godots signal system, I can send signals upward in the hierarchy and to other nodes without needing to do too much setup.  Is there something similar in any of these engines? If not, then that's not too bad - I'm able to implement it myself. 

Hello, thanks for checking out my game jam

Coming from Godot I would probably recommend Defold. It is the closest thing to a full game engine like Unity or Godot. All the other suggestions I listed in the jam description are more code focused. So if you are looking for UI development I would recommend this Defold tutorial. And for something similar to Godot's signals system there is a message passing system, see this tutorial.

Outside of Defold there is also Love2D which is a great framework, which is entirely code based. However. without using helpful extra libraries it can lead to some boilerplate. But you can find a lot of useful tutorials and libraries to get up and running faster:

• GUI libraries
• other libraries
• events