this is because:
most of them also support DNS hijack / force / local enforcement config for firewall
you haven't actually fixed anything, openwrt's adblock simply made sure the secure DNS used by your client was blocked.
you don't really need the package, you need to implement https://openwrt.org/docs/guide-user/firewall/fw3_configurations/intercept_dns.
not getting a cutting edge $3000 laptop only to find out half of the hw features in it aren't supported by Linux, yet.
sorry to disappoint, but hey, at least I know how to disable secure DNS in my OS 