Mineral oil is standard and just plain works. Cheap to boot. Flax seed oil is also an excellent choice.
And yes, wood is actually better than plastic. Clean it off, give a spritz with 50/50 water/vinegar as a spray on cleaner, dry off when done. The tannins in wood act as a natural anti microbial agent. The oil finish repels most of the nastiness anyway. Wood is also self healing and since it gives a little grip to the knife is actually safer to cut on.
Plastic got the nod because of perceived advantage since it can go in a dishwasher hot enough to sanitize or hold up to various chemical sanitizers you don't particularly want on wood. The fact wood doesn't need such in the first place was lost on the "experts".