The below statement is provided in the documentation which isn't very clear to the customers and the majority of them get confused.

You cannot use br-ex, an OVNKubernetes-managed Open vSwitch bridge, as the interface when configuring DNS resolvers.

[https://docs.openshift.com/container-platform/4.13/networking/k8s_nmstate/k8s-nmstate-updating-node-network-config.html#virt-example-nmstate-IP-management-dns_k8s_nmstate-updating-node-network-config]

The change related to DNS servers in /etc/resolv.conf file over nodes in an OVN cluster with the help of NMState is currently not supported. It would be helpful if the statement I mentioned above could be simpler just like I explained. Also, the following RFE is there for this feature.

https://issues.redhat.com/browse/RFE-4104