/var/discourse/shared/standalone is mapped to a volume in the container, all persistent data is stored under there.
docker network ls will list the docker networks, what I see is the default bridge network and two other networks. Containers use the default bridge network unless explicitly told to use something else.
I’ve found some information about the default bridge network no longer providing connectivity to the outside world. I’m speculating but Ubuntu 22.04 may have moved to a version of Docker where this applies, meaning the Discourse container will need to be set up to use a user-defined bridge instead.
I think you can just edit /var/discourse/containers/app.yml and add this to the bottom, then rebuild: (I haven’t tested this, however)
networks:
default:
driver: bridge