Clean your microwave regularly just as you (hopefully) do other surfaces in your kitchen.
I wash the plate and the wheeled thingy under it, and go over the damn thing inside & out w/a hot and

paper towel w/50%+ rubbing alcohol on it.
I’ve been wiping down the nuker, the fridge & its handles, the taps & faucets, the sinks, the stove, and the kitchen counters w/alcohol since the plague began.