It would be very nice to have a feature to sync a folder not only to upload the files or photos towards servers also this feature can remove these file or photos uploaded.
The case is the current app of android allow sync folders but only works to upload new files/photo but if you remove one of these files or photos from your current folder synchronized , these files are maintained in server and are not removed :-/
When you delete a file with the Nextcloud App it should ask you if you want to delete the file just locally or on the server too.
The automatic photo-uploading when you make a photo just copies the photo to the cloud. Deleting photos with the camera/viewer-app should not affect the uploaded photos, so you can have enough free space on your phone for making more nice photos.
So if you want to delete files you have to do it with the NC App.
I think this is a Feature-Request for a Option for real folder-synchronisation like on the Desktop-Clients.
This is what you want?