Rescue system with failed boot-pool and a very old db backup

[g3rt]

After the sudden death of both disks in the mirrored boot pool, I am in need of a way to restore the system to working order.
I am sure i usually backup the system configuration, including the secret seed, whenever I upgrade the system, which was currently at 13.0-U5 (U5.3, I believe). However, the single backup I am able to find now is from 2022, made under TrueNAS 12.0-U8.1, according to the filename. I do have the dataset pool key in json format for the data pool backed up. I do also believe, but am not certain, that the system dataset was on the storage pool.

What is the easiest way to go about it?
1: Install latest TrueNAS and try to use 12.0 db backup?
2: Use a live OS (some linux live usb with zfs support perhaps?) to mount the storage pool and look for the automatic database backup there? Does these automatic backups contain the secret seed?
3: Other solution perhaps?
If the naming scheme for system configuration backups have changed since 12.0 please advise, perhaps I do have later backups but are simply unable to find them.

 

[g3rt]

For anyone in a similar position, solution 1 worked. Turns out a backup with secret seed also contains the encryption key for disks, so no need to restore that manually. Pool imported, and there on the pool was also a more recent backup which I'm now restoring, just to make sure. Perhaps for the future, i should make sure not to delete the config backups from my other computer thinking "it is stored on the NAS anyway"...