This plugin will remove other Volumio instances on the same network from the UI:
The implementation is not done as it should, but from a plugin I do not see another way of doing this cleanly.
A clean implementation will give the user the option to change the serviceName. This way we can group Volumio instances per room/area (like livingroom, attic). Since I can not access this configuration parameter from a plugin (setConf in ControllerVolumioDiscovery is broken) this is not possible.
If one of the core developers of Volumio is willing to make some core changes, I can look into a decent plugin with UI.