I have published to Github and Docker Hub, scripts and a Docker image which should make it relatively easy to run Mailpile on a modern Linux distribution in spite of Python 2.x no longer being supported.
Instructions (and the scripts) are here: https://github.com/mailpile/Mailpile-v1-Docker
Note this is not intended as encouragement for more people to start running Mailpile v1 in production or as their daily driver e-mail client: development on Mailpile v1 has stopped and I do not encourage people to use it. However, some people have no choice if they want to access their old Mailpile e-mails, and these images are provided to make their lives easier.
Any and all feedback is welcome and appreciated. Thanks!