Dropbox online only files with smart preview

[aakraak]

I want to store my photos on dropbox. I use the online only option, to prevent save local disk space. I recently discovered the smart preview function in Lightroom. When I tried this funcion and then made the photos on Dropbox online only, Lightroom says "The file appears to be unsupported or damaged" which is not true. I can still edit the photo's because of smart preview.

I am wondering if it is a bad thing, if I get this error. Is this normal? Is it possible to use Dropbox to store your photos and use Lightroom Classic? 

I looked on the Dropbox forums, but no answer. Does anybody know?

[Per Berntsen]

Lightroom Classic requires that your photos are saved locally.

You can keep your photos in a Dropbox folder (I've done so for years), but you cannot use Smart Sync, which removes the local copy.