I appreciate this effort as a fun project for personal profit, but for readers who'd like this kind of DNS sinkhole, or more general - DNS filtering proxy, there are much easier options. Just search for Pi-Hole or AdGuard Home. They can easily be run on a Raspberry-compatible device, on some routers or NAS devices, the easiest as a Docker container, or even a tiny VM in cloud for a few dollars. They have nice web interfaces and offer great customizations.