If a particular Group has their own Joomla website, then the component can be installed there.

 

An alternative is to host the service on a Joomla Area site, and maintain there the mailing lists for all Groups in that Area (this approach has successfully been adopted by Staffordshire Area, see https://staffordshireramblers.org/mailman/mailing-lists.html). If no Area website exists at all, it is a simple process to create a simple, fully functional, Area site from an existing Joomla template.

 

Yet another alternative is to create a minimal Joomla Mailman site on a sub-domain of any existing non-Joomla site. For example, leave unchanged www.xxramblers.org.uk and create a parallel site mail.xxramblers.org.uk.