For the prosumers that have a homelab (windows server, linux, etc...) why not let us to set the external IP address or use DDNS and then forward all traffic through a DNS server through forwarders. Without this setup my "devices" can't communicate with the DNS servers I have.
I believe the details are already listed out in the Setup Guide
https://my.nextdns.io/<yourconfigid>/setup > Setup Guide > Routers.
You would use whatever resolver you're using in your lab and have it point to NextDNS as your upstream resolver. This would allow your resolver to answer first, and when it can't it will forward the request on to your NextDNS profile accordingly.