Grass is plenty, bark is plenty, dirt is plenty.
those 3 materials can be converted into a self insulating biodegradable sturdy but flexible material which is 60% pure protein by calories, 100 grams of mushrooms having around 22 kilocalories of which 13.2 are proteins, but they can be dried and turned to slabs, bars, loafs or bricks to reduce the volume occupied by water just like dried meat, biscuits or tofu.
Mushrooms do not defecate on your land, they don't spread disease, but actually can be used as healing and prevention. Corona virus came from poultry not mushrooms , Brain eating prions come from cows meat not mushrooms, there's even the famous example of a woman who ate raw pork for 10 years and became a living suit of worms inside human skin, she is more worms than actual person, the worst one can get from eating raw mushrooms is ingesting digestible fly larvae which many cultures eat anyway, and the worst thing is that pork crap contaminates the land with worms ready to infect anything they touch. Mushrooms can grow in 3 dimensions and do not require massive lands to be farmed, it is technically possible to fill one bedroom with mushrooms, on the contrary it's not possible to grow wheat to fill a room, but it needs a forest cut down in order to free farm land. which means you can grow mushrooms in a tower but not wheat, thus saving land.
Ants where the first animals to discover farming on this planet, and they farm fungi, so I guess it is possible for pre industrial societies to farm mushrooms.
But, can mushrooms be converted into bricks, clothing, beams,ropes, tools and armors with pre-industrial technology? I know some people are already building clothing and houses made of mushrooms but would it be possible without modern technology?