I was using Catalina, I think, and on a tech support call we tried to download a Tif and then JPG and it keeps saying originals are not accessable. We went back a version, no luck. I upgraded my OS to Big Sur and still no luck. It says smart previews only in both areas of the info. Please help, I need to send out prints for presents and to clients. This is such bad timing.
Have you migrated a Catalog though or just synced Collections? Migrating a Catalog should upload the full resolution to the Cloud whereas syncing Collections does not.
Anyway, if you have just synced Collections and there are Smart Previews in the Cloud then the options are to either upload the originals to the via the Cloud Based Lightroom (which will overwrite the Smart Previews but retain the edits) or just export from Lightroom Classic if you also use that.