The error you're encountering with the Spine URP shader is likely due to an incompatibility between the shader version and your Unity version. You are using Unity 2022.3.31f1 with the Spine URP shaders version 3.8, which is designed for Unity 2019.3-2020.3. This mismatch can cause shader errors.
To resolve this issue, you should update to a compatible version of the Spine URP shaders. For Unity 2022.3.31f1, you should use the Spine URP shaders version 4.1. You can download the appropriate package from the spine-unity download page.
Here is the direct link to the compatible URP shaders package:
spine.urp-shaders 4.1 2023-10-26 - Unity 2019.3-2023.1
After downloading, make sure to install the package correctly by placing it in the Packages directory or importing it via the Unity Package Manager.
For more detailed instructions on installing and updating the URP shaders, refer to the spine-unity Runtime Documentation: Optional Extension UPM Packages.
