So first of all, why on earth do you want syncthing inbetween this? You save a lot of headache by simply using Nextcloud clients to sync your files.
Nextcloud’s initial use case is to keep several desktop machines (eg your laptop and workstation) in sync, it is what it was designed to do…
But if you somehow want syncthing, keep in mind:
- don’t ever change the files in nextcloud primary storage (the data folder)
- you can change files in external storage, you can configure how often to check for changes but in any case, Nextcloud ONLY checks for changes if you use the web UI, not the client
- Nextcloud has a WebDAV interface you can mount. Use it as any normal network drive - no need to sync, that is done immediately, just like the Desktop client syncs any change you do locally within seconds to the server.
In your setup, you sync from one system to the next, but you have Nextcloud on one to make the files available to the outside, right? If you mounted that folder as external storage and set it to always update the storage contents, what you see in Nextcloud web UI should be up to date with what is in the folder, whatever syncthing does in the background doesn’t matter. No need for a Nc cronjob in case you use the web UI.
If you use the Nextcloud clients it is better to use a cronjob, yes, it doesn’t always check for new files so if the content of a file is changed it doesn’t matter but if files are renamed, deleted or added, you’d have to scan. Again, I suggest to avoid this mess and not use syncthing.
PS props for the drawn picture, though 