hiknapolitano In my project, I could only find the "Outline Shaders URP" scene under "Packages/Spine Universal RP Shaders/Examples",
@hiknapolitano This is the correct scene, no worries.
hiknapolitano but it's unfortunately missing a lot of references for scripts and sprites. Someone who worked on this project before may have deleted a lot of example stuff from the project before me, I guess.
This is not good. If perhaps the shader files have also been modified, that would obviously explain why the outline shader don't work as expected. You should be able to check the modifications of the whole directory (in the main spine-unity package directory, Spine\Runtime\spine-unity\Shaders) in your version control system (git, Perforce, or whatever you're using).
hiknapolitano Are there scripts or external things other than the Outlined materials and their shaders that should exist in the project for them to work properly?
The SkeletonGraphic outline shader file requires some include files, so if any are missing, the respective shader pass will then not compile, which might be the case in your project. You should then see some notes about compilation errors when you have the outline shader active in your scene and select the shader file Spine-SkeletonGraphic-Outline located in the main spine-unity package at Spine\Runtime\spine-unity\Shaders\Outline\SkeletonGraphic.
Also check if the material SkeletonGraphicDefaultOutline really uses the above shader and the shader name reads Spine/Outline/SkeletonGraphic
