Can jitsi be used locally/LAN only?

With the self host/docker variant of jitsi server, is it possible to run everything locally/LAN only (i.e., smartphone, tablets and desktop clients connect & meet without going over the Internet)? If so, what tweaks to the .env and other configs does one need to make to accomplish this? If not possible, what’s the next best way to run everything without exposing much to the Internet and keeping things secure?