element-call/config/config.devenv.json

{
  "default_server_config": {
    "m.homeserver": {
      "base_url": "https://synapse.m.localhost",
      "server_name": "synapse.m.localhost"
    }
  },
  "ssla": "https://static.element.io/legal/element-software-and-services-license-agreement-uk-1.pdf",
  "matrix_rtc_session": {
    "membership_event_expiry_ms": 180000000,
    "network_error_retry_ms": 100
  }
}