No worries, also just to let you know. I have a TrueNAS and a unraid server.
The TrueNAS server has a Unraid samba share mounted. Within TrueNAS you setup a pull task where it copies files from your remote system to keep the directory in sync. Any changes on my unraid samba share are backed up to my TrueNAS share on a predetermined schedule.
You might want to look into the pull task on your TrueNAS which will be a lot easier then trying to push files from your OpenMediavault.
If both servers are running TrueNAS (scale or core) the best way to backup a TrueNAS system to another is by using zfs replication.
https://www.truenas.com/docs/solutions/optimizations/disasterrecovery/
Video to get you started. https://www.youtube.com/watch?v=9gKZOAL7yeE
You could also do the following.
Setup site2site VPN connection of your choosing. IPSEC maybe.
Temporally do the setup of the secondary TrueNAS at Site 1, unless you are sure your Site 2 is good.
Configure the second TrueNAS to Pull data from the primary unit. FYI, pull configuration uses it’s own login credentials is a higher level of security.
Migrate the second TrueNas unit to the site 2. This way you aren’t diagnosing both the Pull config and VPN settings at the same time.
Its apart of a Watercooling setup