RPI Hass Docker installation - unable to read P1 meter via USB

After failing to install Hass via core installation (complete dependancy hell), I decided to give Docker a go. Hmm, this would have saved me two frustrating evenings…

docker run -d \ --name homeassistant \ --privileged \ --restart=unless-stopped \ -e TZ=MY_TIME_ZONE \ -v /srv/homeassistant:/config \ --network=host \ ghcr.io/home-assistant/home-assistant:stable

It works well, netstat -an | grep 8123 shows the port is listening.
And I can surf to the Hass home page and create a local account.

Next step, I have a Landis+Gyr 360. I connected a RJ12 to the meter and plugged the other end into USB port of the RPI.

Ok, now I need to forward the USB0 from RPI to the Docker application.
Here I used the following script, modified it slightly to match the docker install for /srv/homeassistant.

docker run --device /dev/ttyUSB0:/dev/ttyUSB0 -d --name="home-assistant" -v /srv/homeassistant:/config -v /etc/localtime:/etc/localtime:ro --net=host ghcr.io/home-assistant/home-assistant

When I try to add the DSMR integration, it gives the following error.

Is there any way I can check Docker that the USB port forwarding has correctly been setup?
Any pointers in the right direction are greatly appreciated.