Maybe it's better now, but a couple years back I found streaming iTunes movies (I think Apple used Akamai at the time and may still) would not work at all if not using my ISP's DNS servers. So I had to configure dnsmasq to forward CDN domain lookups to my ISP's DNS servers.
I wonder if a good compromise for EDNs w.r.t. privacy would be that instead of forwarding the client subnet, instead have a lookup table mapping the client IP to their ISP's DNS servers, and then insert subnet of the ISP's DNS servers. I suppose it could be any "representative" subnet of the client ISP though.
Also, minor typo in the FAQ answer for "Does Quad9 implement DNSSEC?": "... Note that some variations of our resolver (differente IP addresses) may not provide DNSSEC."
Different has an extraneous trailing "e".