I took the title of the textbox to be the definitive requirement and as my DHCP server (on a Domain controller) does not run on my router (remote access machine) I ended up pointing at the wrong IP address.
I'm not convinced. Pi-hole is a commonly used project for users never having working with networking, it may be even their first Raspberry Pi or even their first Linux project. It is not all that likely that they know what a DNS server is. However, they typically know what a router is.