Software and hardware are increasingly hardcoding DNS servers. If you do use it, block DNS requests from all clients except your pi-hole on your router. Also,

Software and hardware are increasingly hardcoding DNS servers. If you do use it, block DNS requests from all clients except your pi-hole on your router. Also, be aware that systems can still try and resolve IPs using a different mechanism (e.g. if too many people start DNS blocking) or worse hardcode IPs. Pi-hole cannot sort those out. You'll need a more advanced firewall. Something like pfsense or the like.