Your problem may be related to the issue mentioned in this thread:
You have like over 100,000 objects in your profile according to the photo of your sync status screen on desktop. Other users have had issues with slowness syncing with only about 1000 objects on Android
EDIT: Actually this may be irrelevant as it seems if you're not using file system sync then sync operations do not touch the file system. I think the issue I linked was primarily caused by many revisions needing to be deleted and performing the remote deletions on Nextcloud is likely the cause of the blocked sync, due to throttling. From your log there is no evidence that there are revision deletions blocking the sync, and Joplin cloud should be faster at handling many requests as well. Also from your log it looks like over 8000 object have been created locally, so I suspect that all your notes have already been downloaded, but it might be that the notebooks objects which contain most of them have not yet been downloaded, which is why you only see a handful of notes on your device