Two Lustre community groups exist. Whamcloud participates in activities with both groups. Details of their activities can be found at their respective websites - EOFS and OpenSFS.
There are two main Lustre mailing lists, and a second list for discussing Lustre development (features, coding, etc):
There are also several OpenSFS mailing lists that focus on different OpenSFS activities
Slack
The Lustre Slack channel is Lustre Upstream Client.