Follow-up question: what is "option 06"? Where do I set it up?
In any case, here's further details on my setup.
In Openwrt, DHCP and DNS > Advanced Settings, I have the DNS server port as 553 (because Adguardhome takes the port 53).
In Openwrt, Firewall, I have a "guest" zone, to which the interfacte eth1.10 is assigned to. Under Traffic rules, I have all incoming IPv4 and IPv6 from "guest" to "this device" directed to the DNS IPs, port 53. Note: the DHCP works, just the DNS doesn't work.
In Adguardhome, I have the reverse DNS servers set as the IPs of interfaces with th 553 port as set on the first step.
