I'm incubating oyster mycelium in a cupboard. When the fruiting bodies come, and they sporulate, will that endanger the cupboard itself ?
The only way fungus will harm your cabinets or any wood is if that wood is already in a condition that is conducive for being decomposed; it has to be constantly moist, little air, no sunlight. Then fungus will be able to use your cabinets for energy. Mushrooms are the reproductive part of some fungus organisms. Not all.
So not to worry.
Your question is most certainly is within this site's parameters. My opinion of course. Fungus is grouped in the Plant Kingdom. We need to know how to live with fungus just as we need to be able to grow green plants. Where else would you find information on fungus? Great question but this site is careful about the types of questions. Shoot, Gardening and Landscaping cover just about everything! Grins.
I don't think you can use your kitchen cupboards as a fruiting chamber. Once the bags are fully colonized, and they start to fruit you'll need to provide oxygen and light otherwise they won't grow well. Since the bulk of the mushroom is water you'll need to keep misting them which could damage the wood, but without the increased oxygen and light they won't do well.
If the wood is kept moist from misting you might get surface molds developing which you can wipe off.