Usually, you’ll have to login to the admin user of the NAS box via SSH, to setup the UID and GID values – “chown … ” – the NAS boxes usually run Linux …
The simple answer is, setup the NFS Server on the NAS to export the directory where the Linux files are located. The Synology NAS boxes usually have an NFS Server function.Were you using the “ Active Backup for Business” Synology App or, something else? – Possibly the Synology “Drive Client”? I have a Synology NAS with which I have been able to synchronise my desktop computer files using a client rpm package from Synology.