So prepulse rubber, after 100 years in the dragonscape, is mostly useless and has almost all dry rotted into nothing or is otherwise useless. This idea is still in the works so we will have to see how it goes and I wouldn't call it canon yet.

But there is an idea for which drekir could make and vulcanize their own rubber through alchemical means. Sourced either from the root of enchanted Dandelions or Naturally grown Rubber trees (just like real rubber sourcing). Vulcanized alchemically and with natural or magical fires various tribes that have taken the time to experiment with it have made some alchemical rubber. I think while it isn't the easiest thing to figure out some cultures could probably figure out how to do this, particularly in regions where prepulse people were already making a lot of rubber from either material, such as Brazil and on a smaller scale the US State of Nebraska. Not saying it wouldn't pop up in other cultures and other parts of the DragonScape might discover it through experimenting with the world around them but those areas have a lot more of a reason to understand rubber manufacture.

There are some more obvious uses a culture would probably want to do with a primitive rubber, obvious things like using it to make elastic slingshots and slingbows that help a drek get around ergonomic and biomechanical problems that prevents them from using a bow and arrow proper might be a commonly made thing. Various sorts of balls for playing games and sports in the village might be appreciated considering most prepulse balls have been shredded or entirely destroyed by this point. I could also see drekir using this rubber to make gas seals, not many uses for a gas seal outside of containing air elementized mana or alchemicals involve air mana. Lastly using it as an insulator might also be nice, make some sheets of it to layer between the thatch, plastic and bricks of your den to help keep the cold out or to keep the water out.

A more magical application might be its ability to resist or "dampen" magic, pulse resonance of a weaker variety may not be able to get through alchemical rubber and the magical energy of dragon magic may have a hard time transferring through the rubber into the wearer. This might make rubber a popular material for drekir that have to interact a lot with dangerous magical anomalies, users, and entities. A dreamcaller may wear some to protec themselves from a spirit, wanderer or sta, or a drek traversing a voicelake may wear some to keep the resonance from giving them major problems. Likewise if a drek is expecting a mage to get violent then some rubber might serve as a decent armor, just put some street signs over that.

anywho not sure if it'll be canon yet, it's something I feel drekir could do and it could be pretty easily justified overall as drekir try and experiment with the natural world around them to improve their odds of survival. It wouldn't be everywhere nor would it be a game changer, but i am sure it would be a nice resource to have for your village to figure out how to mash some dandelions and insulate your shacks.