I used to pick up “drip dry” pants — linen — imported from I think Taiwan. They wear pretty well, thicker is better. Thinner fabrics in general often don’t have durable seams.
Flax was grown for oil at least 9000 years ago, the processing of linen fiber is first attested in an archaeological context (sez here the Alps) about 3700 BC.
I had a pair of linen slacks , got them in Italy. Very comfortable, especially in hot weather.