There are so many different fungi which are used in the textile industry, unfortunately a load of them are with 'exclusive' designers and companies, so Joe Public can't buy them.   But I did find this one.  Processed in Germany from tinder fungus, essentially the fungus is flattened out, and that's it.

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It's super soft and you really just want a blanket made from it.  To use in garments it is commercially backed with a wood textile and cotton.

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Environment wise... it is essentially an unprocessed fungus, so no impact.