Quad9 has several IPs and different services, see (https://www.heise.de/imgs/18/2/3/1/7/9/4/7/quad9-feature-mat...). For some reason this is hidden on the quad9 website.
Seems they've sunset .11 and .12, but .10 is still up.
dig @9.9.9.11 +short
;; connection timed out; no servers could be reached
dig @9.9.9.12 +short
;; connection timed out; no servers could be reached