After a couple weeks of procrastinating, I finally migrated my NetBox instance from the Ubuntu 22.04 Proxmox LXC old to the new #FreeBSD 15.1 Jail.
The old NetBox instance was still on v4.1.7, because I would have needed to upgraded Postgres 14 to a later version.
Fortunately, the only thing I had to do was to dump the old netbox database and restore it into the Postgres 18 DB inside the jail, and copy all the images from .../media/devicetype-images over.
The Jails runs v4.6.10 and simply running "manage.py migrate" once after restoring the data was all it took.
Now I can finally shut down my Proxmox VE server, as all services have been migrated to my FreeBSD NAS / home server. 😁