This works if you’re having PiHole hand out DHCP on your network.

nano /etc/dnsmasq.d/05-no-pihole-dhcp.conf

Now we need to add the following to the file. You can change to anything you want

# Assign alternate DNS for select hosts
# Set Specific Clients to be affected
dhcp-mac=set:altdns,00:00:00:00:00:00 #Device 1
dhcp-mac=set:altdns,00:00:00:00:00:00 #Device 2

# Set Alternate DNS