Expected Behaviour:
I have installed a standard installation of pihole on a raspberry pi connected to my network via ethernet.
I am using a TP-LINK Deco as a mesh network.
When I set the pihole as my only DNS server in my Deco Mesh settings then I cannot access the internet and the Deco reports no internet connection.
I also get no queries appearing on the web interface.
If I offer a secondary DNS then I do get internet access.
If I set a client on my netowrk to use the pihole as a DNS server then it works as expected.