Upgrading/replacing old jail

I have an old jail that stopped being able to be upgraded with TrueNAS 11.2 (TrueNAS itself is now running 13U6). Something about manifest problem. I also believe that old type of jails have been superseeded by some other type (iocage?).

I don’t want to mess with it unless necessary since it’s working fine (If it aint broke don’t fix it) but I’ve recently been caught out by Veracrypt not being able to unlock drives made before 2014 since they’ve removed all support for the then default encryption method.

So I don’t want when I do a TrueNAS upgrade in the future to find that my jail doesn’t work anymore.

Is there a plan to remove support for old jails?
How would I move old jail into iocage (don’t want to have to reindex 6TB data with Resilio Sync)?

Any good links or info on the above questions would be appreciated.