Can an oil painting be finished with wax to create a matte finish?
Pure beeswax is compatible with oil paint and you can use it as a top coat or "varnish" on oil paints to provide a matte finish.

There are also cold wax mediums and varnishes that you can use with oil paints. They are a mixture of solvent like mineral spirits or turps, pure beeswax, and resins, the same materials you use to make mediums and varnishes for oil painting with the addition of beeswax. These you can work cold mixed with oils, dry pigments, or as a top coat to get a matte finish. In my experience they work fine but do not have the same depth as encaustics. They will take longer to set but will be easier to work with and provide a stronger finish than pure wax.

The curious may want to look at encaustic painting which is painting with pigmented beeswax and gives a distinctive appearance of depth and translucency which using a wax varnish approximates.