Thanks Mariano
On the ReadyNAS forum there was a suggestion that using chron on readyNAS is possible but not ideal, and that the built in ‘systemd timers’ was better. Not sure if that allows anything as fancy as remote directory cleanups though.
Am currently struggling with ‘Permission denied (publickey)’ errors whenever I attempt to connect from ReadyNas to my Discourse server - even though I have added the ReadyNAS public key to the list of SSH users on Digital ocean.
Will report back here if I make any progress, for anyone else trying this.