Grafana linux server vulnerability medium cipher

No, you can’t configure it in Grafana. Ciphers + all TLS configs are hardcoded:

BTW: I don’t see any 3DES cipher ^.

Try to use nginx in front of Grafana and configure ciphers/TLS there.
Related PR: https://github.com/grafana/grafana/pull/7347

I recommend https://github.com/drwetter/testssl.sh for SSL sec. testing.