We are in the process of registering a DotGov.Gov domain and it’s needs the nameservers. I can’t add the domain to CloudFlare because it’s not a registered domain yet. I reached out to DotGov support and they stated that they had many customer that use CloudFlare and that CloudFlare Support would have to manually add the domain and A record for the domain. I tried to initiate a support request but it sends me to the community.
Here is a community post on the exact same issue and a support rep took over the issue from the community post.