// inside client init class
public static boolean isRenderingInWorld = false;
...
void onInitializeClient() {
        WorldRenderEvents.END.register(context -> isRenderingInWorld = false);
        WorldRenderEvents.START.register(context -> isRenderingInWorld = true);
        ...
}
// inside rendering function
void someFunctionToRender() {

  if (ClientInitializer.isRenderingInWorld && FabricLoader.getInstance().isModLoaded("iris")) {
      l = RenderLayer.getEntityCutoutNoCullZOffset(...);
  } else {
      l = RenderLayer.getEntityCutout(...);
  }
}

// inside client init class
public static boolean isRenderingInWorld = false;
...
void onInitializeClient() {
        WorldRenderEvents.END.register(context -> isRenderingInWorld = false);
        WorldRenderEvents.START.register(context -> isRenderingInWorld = true);
        ...
}
// inside rendering function
void someFunctionToRender() {

  if (ClientInitializer.isRenderingInWorld && FabricLoader.getInstance().isModLoaded("iris")) {
      l = RenderLayer.getEntityCutoutNoCullZOffset(...);
  } else {
      l = RenderLayer.getEntityCutout(...);
  }
}