This is what I recently had to do as well. I also had to export the ‘Personal Calendar’ on the phone, import to NC and then sync.
For syncing other things, I wanted more control, so I’m using rclone like:
but I have another endpoint in addition for NC. I organize images, for instance, in folders so simple syncing isn’t for me.
EDIT: [Guide/Hack] Automatic Nextcloud file sync when directory contents change - #11 by nephros is a nice overview fro nextcloud from @nephros