Hit a brick wall. I'm using PiHole on another device as my sole DNS. Guest network devices can't see each other, which means they can't see PiHole. I would think that guest network devices would see the ISPs DNS, but they probably are attempting to see the local DNS through PiHole and being denied access to the device, hence no Internet.

There's no option to configure DHCP for the main network and the guest network independently, so I'm stuck. I can use the ISPs DNS for everything, tracking and ads and all, and service all users (main network and guests), or I can use PiHole for the main network and lock out all guests from using the internet at all.

Also, there's no way to disable isolation for the guest network, so it's very all or none as described above. It would be nice to have some additional options with the guest network configuration.