If you already have a pi-hole and you want it to be your DNS, you can configure the tailscale ip address of the pi-hole server (100.x.y.z) as the global nameser

If you already have a pi-hole and you want it to be your DNS, you can configure the tailscale ip address of the pi-hole server (100.x.y.z) as the global nameserver in the DNS settings in tailscale, and it will route all your DNS queries to the pi-hole. You can also have the pi-hole configured to use NextDNS as its upstream nameserver, and that works very well. Also, you can set up the server as a subnet router, and have access to all your machines on the LAN, even if you can't install tailscale on all of them. Tailscale is truly incredible!