While Penpot officially supports Docker (& docker-compose), Podman is a drop-in replacement of sorts for Docker.
While the official Docker support requires docker-compose, Podman doesn't have a native/first-party conversion for compose files yet.
The ./run.sh file will build out the network, create the containers and mount the necessary volumes.
This is a quick PoC and isn't meant to be the most prettiest solution, but it works.
If you want to kill the containers just run ./run.sh stop.
Since Penpot will generate a new secret key on boot whenever PENPOT_SECRET_KEY is not found in the env vars, it's not a necessity to set one.
However, I would advise if you do to set it in a pod.secrets.env file.
All the envs found in pod.env are from the official docker-compose.yml set up so change accordingly if you like.