@lxs Unfortunately there is still some information missing to be able to help properly.
What render pipeline are you using? Are you perhaps using a URP 2D renderer under Project Settings - Graphics (or potentially overridden in Quality settings) and not a URP 3D renderer? You could share aa screenshot of the Graphics section, plus what exact Inspector settings your assigned Render Pipeline Asset shows. Likely this is a shader vs render pipeline mismatch.
Note that 3D URP and 2D URP shaders are incompatible, and the Spine URP packages provides both, see the documentation here (or in English here).
