I see a trip down the rabbit hole in your future. LOL
I have a custom pi-hole file that is probably also needed.
/etc/dnsmasq.d/02-guest.conf
server=/lan/192.168.2.2
server=/2.168.192.in-addr.arpa/192.168.2.2
Change the above address to your guest lan ip.
edit:
i do have the switch ports 1,2,3,4 aka vlan1 in br0
so i do actually have 1 vlan.
well 2 if u count the wan port vlan2. do not bridge vlan2!
br0 contains wl0 wl1 vlan1
br1 contains wl0.1 aka the guest wifi
As far as the DNS tab in pi.hole
I have conditional forwarding set to the main lan and listen on all interfaces.
Plus so much more on dd-wrt its a lot of work. I am willing to help you if you decide to do it.
You can pm me if needed.