How to animate a texture change?

I am following this tutorial to use multiple textures with a slider to show one at a time. In this case it is being used for a cartoon face.
Except the Auto Keying is failing to create a keyframe when the slider is used and a texture is changed.
How to animate it then?
Ideally in Eevee, but Cycles would be ok.

Thanks guys


As Mobin suggested: Use a Blender driver.