creating FreePBX lxd container image from virtualbox instance

I needed a freepbx lxd image for some test, and since I didn't find it in public image servers (well, default images: one and google search but nothing, I think for licence's issues but don't really know). I tried to create one by installing FreePBX 15 on virtualbox, mounting the vdi (via qemu-nbd), tarballing it, creating a simple metadata.yaml and importing it on the server, but * when I launch it seems to be in a broken state * when I launch

exec freepbxtest bash

it starts but I can see mysql is down, and *

start mariadb

complains about polkit not running What can be the problem? I don't really want to run it as a vm. The lxd host is arch linux.