A friend has the Samsung Frame and I think you can only interface with it via the Samsung SmartThings app. It's quite closed. So you need an online thing for the TV and then you upload it into their app.
Yep, it's very locked down, and Art Mode behavior is often anti-user to promote their $10/month Art Store subscription. There are limited matting options and I believe it intentionally crops photos incorrectly, even if you upload in the correct aspect ratio. It also takes about a minute to scroll down to 'User Art' sections with how slow their UI is.
Their Art Store promotion is annoying persistent but not actually required if you put images onto a USB and have it slurp them up; all you need to do is ignore their requests for subscription when setting it up. All that's required is to resize them to full screen with your own matte, or you can just crop the images to the right aspect ratio. Depending upon your desire for fidelity, you could also use ML image extension to get the right aspect ratio.
This doesn't get around all the other annoying bugs in the firmware of course.
They make it superficially closed but it's pretty simple to get around it with a USB drive. Really all you have to do is ignore their subscription system and size your images to match the screen.
