To disable interpolation in Unity for Spine animations, you can adjust the update mechanism to mimic a stepped frame rate. Here are a few methods to achieve this:

1. Adjusting Delta Time in SkeletonAnimation:
   Modify the SkeletonAnimation component to update the animation at fixed time intervals. This can be done by accumulating delta time and only applying updates at specific intervals (e.g., 1/30th of a second). Here is an example code snippet:

      private float accumulate;
      public void Update(float deltaTime) {
          accumulate += deltaTime;
          float fps = 1 / 30f;
          float step = accumulate - (accumulate % fps);
          accumulate -= step;
          step *= timeScale;
          skeleton.Update(step);
          state.Update(step);
          state.Apply(skeleton);
      }

2. Using a Custom Script for Stepped Updates:
   You can create a custom script to control the update frequency of the Animator component. Here is an example script:

      using UnityEngine;
   
      public class SteppedMecanimUpdates : MonoBehaviour {
          Animator animator;
          float timeSinceStep = 0;
          public float timeStep = 0.5f;
   
          private void Awake() {
              animator = this.GetComponent<Animator>();
          }
   
          private void Update() {
              timeSinceStep += Time.deltaTime;
              if (timeSinceStep > timeStep) {
                  float remainderTime = timeSinceStep % timeStep;
                  float appliedTime = timeSinceStep - remainderTime;
                  timeSinceStep = remainderTime;
                  animator.speed = appliedTime / Time.deltaTime;
              } else {
                  animator.speed = 0;
              }
          }
      }

3. Disabling Interpolation in the Spine Editor:
   In the Spine editor, you can turn off interpolation by deselecting the Interpolated button in the Playback view. This will show you how the animation looks without interpolation.

4. Rendering with Nearest Filtering:
   At runtime, ensure that the rendering is set to use nearest filtering instead of linear interpolation. This can be done by adjusting the texture settings in Unity.

By implementing these methods, you can achieve a non-interpolated, stepped animation look in Unity.