Little update:

The reason I bought the Dylos is that I had previously bought one of those ~$40 "air quality meters" on Amazon (e.g. https://www.amazon.com/Zetiling-Dete...dp/B07SD5HJ3Y/), and thought it was inaccurate because it was reading insanely high levels (60,000) inside my house and basically zero in outside air. The Dylos.... did the same thing :/

I have no idea why that would be the case - I have no carpet, pets, or other obvious sources of fine dust, but running the furnace fan (with a MERV 12 filter in it) for a few hours brought the count down to 100 (on both meters). I'm surprised.

My conclusions are:
-those little Amazon air quality meter cubes have very good correlation with the Dylos.
-I continue to be unimpressed with the build quality and usability of the Dylos. I bet it was neat a decade ago when there were no other options, but there are cheaper, better options, today.