OpenNIC

https://www.opennic.org/

IPv4 DNS Server:

185.121.177.177

169.239.202.202

IPv6 DNS Server:

2a05:dfc7:5::53

2a05:dfc7:5353::53

The DNS servers listed here for OpenNIC are just two of many in the US and across the globe. Instead of using the OpenNIC DNS servers listed above, see their complete list of public DNS servers here and use two that are close to you or, better yet, let them tell you that automatically here. OpenNIC also offers some IPv6 public DNS servers.