Feel free to split this off, maybe to Web Tech or Security?
Well have gone at least partially back into the weeds:
First off, big surprise, not using Cloudflare for DNS, using Quad9. (Resolvers listed are both Quad9). Not sure why I thought that was the case. Most likely because I have two different Asus routers running Fresh Tomato. Might have been confusing the current one with the one not in use, which could have been set to Cloudflare DNS as a compromise: dnscrypt-proxy used to be an option in earlier versions of Tomato, but no longer available, and also, for various reasons, no longer wanted to use OpenDNS, which I used use for any number of years. Have screenshots, but only way to tell for sure is to put the other Asus back in service and see - not quite ready for that.
Not sure how much further into the weeds you want to go, but current version of FT is FreshTomato Version 2020.2. Screenshot of part of Basic->Network page:
Some curious results running FT with and without Stubby enabled (DNS over TLS): with DNSCrypt-Proxy on the Macs, dnsleaktest shows all resolvers at woody.net (in NY), which is completely kosher and expected for Quad9 resolvers, but running dnsleaktest on an iPad Pro (a much later one, my wife's, running the current v.1.5.4.1, not my ancient one running iOS 9.3.5) with Stubby enabled 2 woody.net resolvers show - expected - along with 3 in the Netherlands. Not sure if this is a leak or not. But with Stubby disabled, I'm getting all the woody.net resolvers that I see on the Macs and none of the ones in the Netherlands. Big question mark around Stubby.
Ran several tests (tenta.com/test/ and
https://www.cloudflare.com/ssl/encrypted-sni/#results) to check if DNS is encrypted, at least TLS, with and without Stubby enabled. Tests are inconclusive, both on the Macs, which I'm 100% certain has to be using encrypted DNS, and on the newer up to date iPad. Even with Stubby TLS enabled, the tenta one shows as TLS false on the Macs. (Both tests for Mac and iPad do show DNSSEC enabled). So not sure what to make of all this. Perhaps you know of other tests for DNS encryption which might be more solid or reliable?
EDIT: Also ran this one
https://dnscheck.tools/#basic, both on Macs and iPad, with this result: "Great! Your dns responses are authenticated, protecting you from certain attacks!" Whatever
dns responses authenticated is supposed to mean.