You can also do some neat things with "--ephemeral" and "--volatile" to basically overlay the image (or a subset) with tmpfs; any changes to those overlays will be lost when the container is brought down. The specific mount points can be controlled in greater detail via "--tmpfs" and "--overlay".

https://0pointer.net/blog/running-an-container-off-the-host-...

I'm not sure how easy that is to customize in Podman.

Containers already are mutable on all popular runtimes. “Immutability” comes from destroying and recreating them from their image, but there’s nothing forcing you to delete/recreate them, and indeed that’s not even the default behavior.