Start with a email list and then try to get together in a pub or somthing like this on a regular basis.
If the LUG gains ground begin to look to some place where you can get together and eventually keep some hardware.
If possible, once the LUG has some regulars, look into joning some events, maybe as guest at a booth
Back at the time I used Mailman, it have a web interface and it should be easy enough to install on every distro. For example, KDE’s mailing lists are handled with it