Do you think I can help you work on that? Or would you prefer doing the initial branch resurrection? Anything I need to know before I start?

Alright, I resurrected your branch to the best of my understanding. I hope it's more Lazarus than Reanimator.

https://code.launchpad.net/~abompard/mailman/subpolicy

All tests pass, but there's still a missing part: the new attribute in the MailingList table must still be actually written as a column, and an Alembic migration script must be generated. I'm going to do that in the next hours (or maybe on Monday), but in the meantime this branch only contains your former code, with minor adaptations. Could you check it out?

Thanks! Aurélien