"downloaded-smart-previews" folder appeared in my download folder

[Wurstkrapfen]

And it contains 10 recent images I have the originals in my catalog for. Why would LR Classic download and store smartpreviews, they are supposed to be in the cloud, I don't need them on my HD where I have the originals.

What is this mess? What happens if I delete them in LRC?

[JohanElzenga]

Did you change the catalog that is synced? Lightroom Classic can sync only one single catalog. If you enable sync of another catalog, then the current sync is terminated. Images (smart previews in case of Lightroom Classic) that are already in the cloud will be downloaded to the new catalog, unless Lightroom Classic understands that they are the same as originals already in that new catalog. So what seems to have happened in your case is that 10 images were not recognized as such, and so they were downloaded from the cloud.

[Wurstkrapfen]

Didn't change anything. 

[john beardsworth]

This also happened to me, and I have no idea why. Just check that you do indeed have all the originals, and delete the folder.