Pi.hole doing its job. I've got 2 instances running, one on a Pi Zero W 2, one in a docker container on the NAS. I think my kids not seeing quite so many ads online was worth the cost of the Pi Zero a thousand times over...
If you want to set up Pi Hole on your network, I wrote a blog post about how to do that a while ago: https://markus.hofer.rocks/pi-hole-pi-zero