OK folks, I've got a solution for this, to allow guest clients to reach dns server on main network. For those that are not afraid of some networking voodoo. (TL;DR - apply the persistant config...

All, The workaround proposed by TP-Link DOES work, to an extent... Setup: PrimaryDNS = local AdGuard server IP. SecondaryDNS = router IP OR internet DNS server IP. What will happen: Client on Main...