You can install and run pkgs in an embedded install via unionfs_mount. I have done this for over 12 years (as of mid-2025) without any problems whatsoever. No jails or VM, and it's quick and easy to set up.

INSTRUCTIONS:

1. Choose one of your data discs (NOT system disc). Mine is /mnt/HDD.

2. Enter the following commands (change the name "extensions" to whatever you choose):

cd /mnt/HDD
mkdir extensions
mkdir extensions/usr
mkdir extensions/usr/local
mkdir extensions/var
mkdir extensions/var/db
mkdir extensions/var/db/pkg
mkdir extensions/var/cache
mkdir extensions/var/cache/pkg

1. Then go to "Command Scripts" and add the following commands in this order (all PostInit and usually the first commands). They're all important!

rsync -a /usr/local/ /mnt/HDD/extensions/usr/local/ 
mount_unionfs -o rw /mnt/HDD/extensions/usr/local/ /usr/local/
mount_unionfs -o rw /mnt/HDD/extensions/var/db/pkg /var/db/pkg
mkdir /var/cache && mkdir /var/cache/pkg
mount_unionfs -o rw /mnt/HDD/extensions/var/cache/pkg /var/cache/pkg

1. Of course, you should modify the above commands to reflect the name of your selected data disc and the name you choose for your primary directory (in my case /extensions)

2. Reboot XNAS

You should now be able to add (and later upgrade) all desired pkgs, and they will remain and operate the same as if you did a full install.

You might hear of the so-called "dangers" of unionfs_mount - THEY DON'T APPLY TO AN EMBEDDED INSTALL, which by its very nature makes it impossible to screw up your system. Should there ever be any problem installing a package(and I've never experienced any), all one has to do is disable the command script items and reboot for a "clean" install.