Mailman 3 is acceptable, imho. It's been a few years since I worked with it, but I was able to design a reliable public instance of it (https://mailman.haskell.org) with a few days of effort, including the migration from mailman v2.

Mailman 3 is horrible, which is why some folks have ported Mailman 2 to Python3.

https://github.com/jaredmauch/mailman2-python3

Same here — I think I set Mailman 3 up in a day, although I was already familiar with setting up the mail (Postfix) part.