Let me start by saying- Lightroom-Classic was not designed for Cloud syncronization, and this hasn't changed.
Using Lr-Classic YOU are the master of your camera files stored locally in your system ("Local Data") and indexed in your local Lr-Classic Catalog.
With the introduction of the 'Cloud' version "Lightroom", Adobe added some sync capability to Lr-Classic, but it is, and always will be, limited- namely-
1) Lr-CLassic will only sync proxy (Smart Previews) up to the Lightroom Cloud from files in a synced Collection. The Lr Cloud must not be considered as a 'Backup' for your original full-size files, and Lightroom-Classic cannot place them in the Lr Cloud storage.
2) Lr-Classic will automatically, and without being selective, download all and any files that may have been imported to the Lightroom Cloud ("Data in the Cloud") by 'Lightroom Mobile' apps (iPhone, iPad, Android, PC or Mac with Lr-Desktop).
If you are wanting to use Lightroom (Cloud version) as the 'Master' of your full-size photo files, then you have to accept that Adobe will store and manage the files in the Cloud.
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