Abhilash maintains a very complete and well-documented container deployment for Mailman 3, but when I was setting up my environment a few months ago I wanted to build on top of RHEL 8 as well as use a database instance shared across multiple applications. So I ended up creating a bare-bones container image that suited my needs and was closer to just doing a simple local install, but keeping the isolation, reproducibility, and rollback benefits of running as a container.
I've been meaning to polish it up and share in case it is useful to others, but finally recognizing that I likely won't get to that soon I've just put it on GitHub here: [ https://github.com/jeredfloyd/mailman-container | https://github.com/jeredfloyd/mailman-container ]
Doing a "podman build" of this should result in a container image that is very much like the result of doing a venv install. This uses the Red Hat Universal Base Image (UBI), which can be freely redistributed, gets upstream security updates, and is eligible for support on a paid RHEL subscription.
--Jered