EDIT:
DON’T
forget this post. My whole¨problem was TrueNAS being 13.3 and FreeBSD only supports 13.4.
But TrueNAS can set a jail up as 13.4, at least a Clone jail.
I had problems with a Basejail setup.
You can run a FreeBSD 13.4 jail on TrueNAS 13.3 without any problem.
I find that now I can…
When I first tried, selecting Release 13.4 in a Basejail creation failed with long and complex error messages.
Today I tried Clone jail and that worked…