There are a few companies in this space, notably Ecovative, who have been trying to make mycelium-based packaging for almost two decades.

The problem is that it takes around 7 days for each piece of packaging to "grow", and the finished part is heavy and not compressible so it adds significant cost in manufacturing, storage and transit. And these costs don't get any better with scale.

For those reasons, mycelium packaging hasn't seen much adoption beyond being used as a marketing story for high-priced small goods. Environmentally forward companies have tended towards paper-based solutions like molded fiber.