Reconfigure cipher suites in services/loadBalancer

You should be able to define the external cipher suites for entrypoint (doc):

# Dynamic configuration

tls:
  options:
    default:
      cipherSuites:
        - TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

But it seems there is no dynamic config for the internal requests (doc, reference).

Note that you can check the changelog on Traefik Github.

Maybe open a feature request on Traefik Github?