Thanks
@billyjoebob007. I bought a couple of cheap-o dongles off Amazon. One worked, but was a little staticky. Another didn't work at all, and my Note gave me a message that I'd attached an unknown USB device. Today I accidentally found a super-cheap option that works great:
https://forums.androidcentral.com/e...b_c_headphone_adapter?hl=en-US&token=qGEvc5Hc
This USB-C to 3.5 mm dongle works great. My Samsung AKG NC60 headphones (from the Note 9 preorder) sound just like they do when connected to a built-in jack, and there is no static whatsoever. What's even better is that while they are $12 on Amazon, you can get them for $7.39 at Target right now. No need to order delivery. If you have a Target store nearby just walk in and pick it up.
Obviously I want to have a few of these, and I want to know what my options are. The Apple store offers USB-C to 3.5 mm dongles for just $9, surprisingly the same price as their lightning-to-3.5 mm dongles. I'm going to pick one up next time I'm at my local Apple store and see how that is. Ironic that I'm buying an Apple product to deal with a Samsung deficiency which was instigated by market forces from Apple.