Thanks for the package, we will get back to you as soon as we've figured out what's going wrong.
In your scene you are combining a normal 3D point light with Spine's URP 2D shaders - this will not work, also not with Unity's own URP 2D shaders.
Also, at the Camera Inspector settings you are using the normal Forward Renderer and have no Render Pipeline Asset assigned under Project Settings - Quality - Rendering.
Please familiarize yourself with the Universal Render Pipeline in Unity in general first and read the corresponding documentation or videos before combining it with Spine. The scriptable render pipeline requires a bit more setup.
Perhaps the Render Pipeline Asset was originally assigned but the reference lost after import. In general it is not recommended to move the UPM package content into the Assets directory, instead it should rather be added as described in the spine-unity instructions here:
spine-unity Runtime Documentation: Installation
This guarantees that the package.json file is evaluated and that any dependencies are resolved.
