Can you apply wax or sealant over ceramic coating?

Yes, but it is rarely worth it. A cured ceramic coating has very low surface energy, so many waxes and sealants struggle to bond to it and may wear off within a few washes. While it lasts, the wax or sealant changes the surface's water behavior and feel, and its own durability becomes the limiting layer, so the car behaves like a waxed car until it wears off. Some waxes also attract more dust than a bare coating. To maintain the coating's performance, use a topper made to bond with ceramic coatings; use wax only if you specifically prefer its look.