The question is how to update or recreate my OMV6 config?
You only had to run omv-release-upgrade and the systems would be updated from Debian 10 to Debian 11 and OMV5 to OMV6.
If you still have the previous system on the SDcard, do it that way.
If you destroyed the previous OS and flashed a new IMG to the SDcard, then your SOL.
If I recreate the filesystem via web, I suppose it will destroy the disk filesystem to create a new one. Is this correct?
No. Once you go to the Storage--> Filesystems page, click on the arrow and select MOUNT (do NOT select create).
Your drives will be mounted and the config.xml populated with the drives.
I'm trying to "import" the omv5 config.xml part of the node conf.system.filesystem.mountpoint to omv6 with the command 'omv-confdbadm update', but I get a dictionary error. I suppose it needs a kind of migration before updating. I've seen the postinst procedure of the openmediavault package does that. Could I use safely this script to update the config file (or parts of it) to from omv5 to omv6 format?