Unknown Horizons/Godot source?

I try to build Unknown Horizons from source but I get this error:

Error: Can't find the Godot editor. Can't build.

I downloaded Godot 4.2.2 for my x64-GNU/Linux but I can't install it. It is meant to run wherever you downloaded and extracted it.

Also I can't find the Godot sourcecode from their webpage.

(I'm using Xubuntu 22.04 which seems to have only Godot 3 in its repos.)

How do I

Peter get the Godot 4 sourcecode?

From their GitHub.

For the second question, i am not sure. But, you could just get the latest Godot binary and open the source project and build it from inside godot.