Are you using DHCP ?
Either set your DHCP server (probably your router) to give out the pi-hole address for DNS.
Or set your Linux Lite machine not to use DHCP and manually assign fixed values to suit your set up for
IP Address
Mask
Default Gateway
Sorry - I don't know where to set those parameters within my Linux Lite network settings
I do have the ISP router configured with the PI Hole IP - but it didn't work.
However - after some extensive digging around online - any playing with several options - I believe I have one that will work.
I added a line to the /etc/network/interfaces file
The line is like this: dns-nameserver (Pi-Hole IP address here)
Now at system startup - this IP address is added to the Network DNS list.
And is the first item on the list.
So I think that will do the job.
Thanks!