@harmonyp You almost had it, just use the raw zvol:
$ virt-customize -a /dev/zvol/zfs/vm-104-disk-0 --install netplan
[ 0.0] Examining the guest ...
[ 2.1] Setting a random seed
virt-customize: warning: random seed could not be set for this...
I needed this to work on a OPNsense VM. Here you need to add:
if ( "`tty`" == "/dev/ttyu0" ) then
set old=`stty -g`
stty raw -echo min 0 time 5
echo -n "\0337\033[r\033[999;999H\033[6n\0338" > /dev/tty
set input=$<
stty...
For reference, tooling to directly import such exported OCI image as LXCs is being worked on: https://lore.proxmox.com/pve-devel/20250709123435.64796-1-f.schauer@proxmox.com/