We go to Denver every couple of months to buy supplies.
So far there's been no shortage of DEF in the Denver Area. In fact, no shortages of any of the things that we see on the internet or hear on the "news" services from "experts". We just don't see it here. There occasional backups - like lumber for twice the price at HD, but it's already back to normal price. Buying monthly, we don't see any difference now from years ago. Some things are always short and overpriced. But so far we haven't seen any real shortages of lumber, building materials, tractors - new and used, toilet paper, machinery parts, oil, groceries, fuel, or DEF.
But that's just here in the middle of the country where everything comes in by truck. It may be different other places...or it may just be that stories about shortages are in style right now.