I reached out to one of our suppliers, and she says that she's still able to place stock orders of MIXE1000, so she doesn't think it's discontinued. She texted one of her contacts at Avient to see if they've got an updated list of discontinued products, and I'll update y'all with what they say.
If they're going to discontinue it, fine, just as long as there's some sort of substitute/equivalent and that information is communicated in a timely manner.
