Try setting UseDNS to no in /etc/sshd_config or /etc/ssh/sshd_config.

Sometimes, Docker’s internet connectivity won’t be working properly, which can lead to a number of obscure errors with your applications. In my experience, this is usually because DNS lookups are failing in Docker images.

Are you looking for an alternative DNS provider that is open and democratic, are you concerned about censorship?

$ dig whoami.akamai.net +short