Okay, I find myself with some time now, so here are my thoughts:
Regardless of what software you use, a forum is better than a mailing list for this sort of thing. Moderation, editing, categorisation, formatting - all better.
We chose Discourse 3 years ago because it seemed the most actively developed and user-friendly. It has an API (rather poorly documented, it has to be said, but it is how the JS front end communicates with the Ruby backend, so is always being “dogfooded”) so it can be driven by 3rd parties. It also has good email support (the devs maintain that email should be supported as a 1st-class interactoin method). The dev/user community at meta.discourse.org is excellent
It also supports 3rd party login (twitter, facebook, google, yahoo, github, instagram) which is great for encouraging guests to post.
Permissions (and linking them to our membership system) has been the most important factor I think. Being able to restrict parts of the site to paying members, and allowing various permissions groups to have @handles is impossible with a mailing list.
As for organisation, we suffer from Category sprawl, which is a familiar problem for all forum owners. We could probably slash their number in half and not feel a thing Tags are enabled, but nobody uses them. IMO, they need curating to work properly and nobody has time for that. General, Private, Off-Topic, Events and Admin is probably your minimum viable set of Categories.
Discourse does have some idiosyncracies - many due to the devs’ aim to encourage high-quality conversations. This can be annoying when you have a pre-built community who don’t need persuading. So you can turn off settings for flood control, minimum post length, duplicate topic titles etc.
Trust Levels are a neat idea. They basically grant “soft” moderation powers to very regular users. Via the API, all paying members are TL3 by default (can move topics and edit titles). You can effectively disable the system by setting the thresholds to ludicrous values.
We’ve done some CSS edits (there is a theming system so you can keep all these edits in one place - they’re non-destructive). Mostly to remove parts of the UI that are only really useful for large forums. You can also use the theming system to insert JS into the /head of every page., which allows for some neat hacks.
Administrating it is part painless, part painful. If you can do it from the Admin pages, it’s a joy, but if you need to install/remove a plugin, or do other low-level malarky, you’re off to the command line. It runs in a docker container, which needs to be rebuilt for evey plugin install/remove. Can take 15m or so. It’s a sophisticated bit of software, not a handful of dumb php files that you can hack at with Notepad.
I’ll leave it there, or this will get hard to read. Long story short: I would recommend it, despite its flaws. I’d be happy to talk more, but I’m off on holiday tomorrow morning. @tomnewsom me on Telegram next Sunday
If you’re in a rush, then I suggest spooling up a cloud server, installing the software and inviting a handful of users to kick the tires. Send me an invite if you do!