Yep, it's supported, but it's not necessarily easy to upload the files.

You can only use a mobile app or the web interface to drag and drop files...

Is that true? Visiting the site [0] there is a sections that says:

   Desktop - Install the Cloud Drive application for PC to add photos from your computer. Download for PC.

It does warn though that:

   We're currently working on a Cloud Drive application for Mac. 

[0]https://www.amazon.com/clouddrive/primephotos

This was going to be my question. It says it supports .RAW, but does that mean it supports RAW files in general (i.e. CR2, ARW, NEF, etc.)?

If so, this is a huge thing for me. I've been looking for somewhere to back up 2TB of RAW files for a long time, but there's nothing out there that's affordable/trustworthy enough that i've found.

I was going to buy this: https://www.zoolz.com/Zoolz_Home but if Amazon can support .DNG files it is easier.

Would be curious to hear if they're using some sort of authentication for the client (ie. private key) as a way to bottleneck that. Would suck to have to relay everything through a smartphone for now... but there's always a better way.

I believe it's either phone OR drag/drop into a browser from a desktop, so just no client side Amazon app at the moment, maybe to keep everyone from installing it and setting it to backup everything on the initial launch.

EDIT: Nevermind, I'm now reading your comment less as "only smartphone available" and more as "use the smart phone app as a proxy"