I'm experimenting with using collections in Lightroom Classic as a way of publishing the contents for various shoots. That much is straightforward. Create a collection, add photos to it and click the sync icon to the left. That all works as expected.
For some reason however, LR decides to arbitrarily upload photos that aren't contained in any collection. I can stop synching of course but the uploads resume as soon as I re-enable it. This is a deal breaker for a number of a reasons. Any idea why this happens?
Are the photos that are syncing that are not in a collection mobile photos?
In your Preferences > Sync tab have you specified a location for synced photos?
Yes, photos are being uploaded that are not part of any collection.
The sync tab specifies a "mobile" folder but the photos that are uploaded are not located there.