I'm using quads for an object, but when I use the subdivision surface modifier or even select "shade smooth" it gives these weird stripes. I have no clue how to make my object smooth now. I've checked all my normals, I've tried converting to tris and back, no luck there either.
It may not be apparent in some views, but if you check face orientation your normals are inverted on half the mesh in a striped pattern.
A recalculate outside with everything selected should fix this.