Force sync of full resolution images to the cloud

One word of warning if you choose method 2: When you use 'Add Photos' in Lightroom you must import the original photos, from exactly the same location as they are in Lightroom Classic! When I first tried this, I thought it was easier to select the photos I wanted to have as originals in the cloud, export them 'As Original' from Lightroom Classic, and then import these 'original copies' in Lightroom. That won't work however. In that case Lightroom will consider them as new photos, so you'll end up with duplicates.

Thanks for your quick response. I'll try your second suggestion. Do you know of a document that explains the syncing logic? I seem to have mixed results of what gets synced and what remains a Smart Preview. Thanks so much.

Lightroom Classic syncs smart previews to the cloud and I assume you are talking about synced collections in Lightroom Classic. To get the originals in the cloud there are two options:

1: Install Lightroom (desktop) if you have not already done that and migrate you Lightroom Classic catalog. It is advised to stop using Lightroom Classic after you have done that.

2: Install Lightroom (desktop) if you have not already done that and import ('Add Photos') all the photos that are synced as smart previews. Lightroom is intelligent enough to discover that the smart previews already in the cloud (and so in Lightroom) are the same photos, and will replace the smart previews by originals.

To answer you last remark: the cloud is not intended as backup for Lightroom Classic. It is intended as a different ecosystem, and Lightroom Classic just happens to have some limited sync options that are kind of 'left overs' from a time when there was Lightroom Mobile (and so a need to sync) but not Lightroom desktop.