Hi,
I added two custom DNS servers to Pi-hole under DNS Settings. My question is whether they are activated automatically, as I can’t find any option to enable them like with the default DNS servers.
Thanks in advance.
There is nothing to be activated.
When you add multiple upstream DNS servers, all off them will be used.
From Pi-hole point of view, there is no distinction between the upstream servers selected by a checkbox and "Custom DNS servers". All of them will be stored as IPs and used.