Reviving an old thread but...
I can confirm that Samsung DeX for PC works with my Note 9 (SM-960F) and my 2019 HP Spectre 13.1 (Windows 10 Pro).
My Note 9 is a dual-sim unlocked model for Asia so I received the Android 10 and new UI update a few weeks ago.
In order to run DeX for PC, you have to install the Dex program on your PC first. I use the Japanese site but I think I found the US one: (EDIT: I CANT POST LINKS YET)
If you just search "sansung dex pc" on Google, it should show.
I simply connected my Note 9 to my laptop without using a dock or PD and it worked fine. In my opinion its a pretty nifty feature and I'm happy to be able to use it. Your Note 9 desktop will appear in a window on your PC screen. Pretty much works like a VM but you can drag and drop files to and from your PC and Note 9. I find it nice for that and being able to type messages into apps like LINE while doing work on my laptop. Funny thing is that my laptop is touchscreen and it works well with DeX.
One thing to note is that the fps on the Note 9 DeX window on your PC screen will be around 30fps. Its not bad, but you will notice it being slower. If you are just using this DeX function to message, transfer files, and check notifications, I think its great. But playing games and watching videos off your Note 9 this way may not be so great.
Anyhow, very pleased that the DeX for PC made it to Note 9. I think it really helps with multi-tasking!