ну в доке ж все написано. на стандартном порту 2379 где обычно mTLS включен. можешь дополнительно открыть optionally on locations given by --listen-metrics-urls. без авторизации
Since v3.3.0, in addition to responding to the /metrics endpoint, any locations specified by --listen-metrics-urls will also respond to the /health endpoint. This can be useful if the standard endpoint is configured with mutual (client) TLS authentication, but a load balancer or monitoring service still needs access to the health check.