More information on Discourse:
 
Discourse is a forum software that has multiple ways to access it: web, native apps, and email. It's not a mailing list software with a web frontend.
The interesting (to me) parts are:
 - 2FA instead of Mailman's plaintext password
 - real moderation tools, that can scale with the community and encourage civility and code of conduct compliant behaviour
 - anti-spam measures
 - open source software (kind of a pre-requisite)
 - good UI for reading and replying to topics
The Fedora (Silverblue) and Ubuntu communities already use Discourse, for instance; the SDL community also does.
Ciao,
 Emmanuele.