I have Unbound blacklists in place which filter some ads. Now one device shall have access to some of the blocked DNSs. I have created an alias with the respective MAC address of the device. How can I make Unbound deliver the correct DNS resolution if the request is coming from "the" device from the alias?
I don't believe the current DNSBL functionality has that ability. You would have to switch to either something like AdGuard or PiHole in order to have client specific filtering.
Another alternative is to just pass your upstream DNS server to that specific client in the DHCP settings so that they could resolve that way.