To load-balance conferences across multiple FreeSWITCH servers, it's a bit trickier than regular call routing because all participants need to join the same conference instance. If you just route calls to the same conference number from different servers, each server will create its own isolated conference. To allow participants from different servers to communicate, you’ll need to set up conference cascading—essentially linking the conference instances together between FreeSWITCH servers, typically using SIP trunks or bridging.

Kamailio can help route conference calls to the right FreeSWITCH server, but you’ll need to ensure all participants join the same conference instance. For large conferences, you might want to route all calls to a primary server or use cascading to connect multiple servers together.

In short, while Kamailio can load-balance incoming conference calls, you’ll need to implement cascading or link servers together to manage a single, unified conference. For scaling, you may also want to consider using media relays or distributed processing to handle the media between servers.