DNS filtering issue

Maybe another approach would be to try throttling the network using SQM. The idea being that if the user-experience of accessing sites / content that were bandwidth intensive was not favorable (degraded), the users would simply give up trying to access such sites from that network and stick to basic web browsing.
Here is another post that touches on the subject.
https://forum.openwrt.org/t/secondary-wi-fi-access-point-network-throttling/99752