[qbasic_forever]

There are polypropylene waterproof fabrics, particularly Frogg Toggs brand gear is popular in the ultralight world: https://www.froggtoggsraingear.com/technology.shtm

They're good jackets in my experience--truly waterproof and breathable like goretex, and very inexpensive. They are very very fragile though and easily rip or tear open from any sharp objects, like getting poked with a branch. As I understand it's basically like tyvek house wrap material but made into a more flexible material for clothes. Goretex stuff is more durable in my experience.