Does this need special rights? If it's "just" a docker image or two, I can host that. (Ancient machines but a decent connection, so no real running costs to me).

As you imply, the main problem with MUC vs Mailing List is asynchronicity and form, so maybe a forum system which is also a mailing list would satisfy a lot of people.

I also wonder if it'd be useful for the IETF, which has similar struggles.

Maybe grab me privately and we'll see what we can do.

Dave.