In the meantime, I moved to the Remote Backup Add-on, which also create a full snapshot. Difference is that it uses SCP to do the copy to the remote location and I also feel that the Remote Backup Add-on is much more difficult to configure.
So despite me maybe not using this add-on anymore, I still feel this change to copy the full backup folder or to create snapshots instead of just taking the /config folder, is still valuable.
I am in a long way to try using iBrew. Having repository for iBrew in add-ons I do have this FTP-Backup add-on as well. Unfortunately, supervisor logs still report WARNING (MainThread) [supervisor.addons.validate] Add-on config 'startup' with 'before' is deprecated. Please report this to the maintainer of FTP Backup
So I am reporting;)
Is there a chance to correct it?