Failed to create folder marker: permission denied

Setup: Syncthing TrueNAS app on TrueNAS. Attempting to sync a NextCloud folder throws this error:


2025-02-26 16:24:40: Failed to create folder marker: mkdir /var/syncroot/Documents/.stfolder: permission denied

2025-02-26 16:24:40: Error on folder "Documents" (documents): folder marker missing (this indicates potential data loss, search docs/forum to get information about how to proceed)

How can I go about fixing this please?

Note that the /var/syncroot address is mapped to TrueNAS’ /mnt/NextCloud/data/dad/files, hence /var/syncroot/Documents is NextCloud’s “Documents” folder.

An error in creating a folder marker seems to always be about file permissions for the user that owns the Syncthing process.