Private DNS Android not connect
I'm using a private dns configured on android running version 11, and when i'm using a mobile network from "Claro Sa" in Brazil it's appear on configuration that's no connection in the private DNS, only in wi-fi the NextDNS private DNS connect.
Nextdns via PrivateDNS feature in A11 uses DoT protocol. Your wifi ISP may support DoT protocol but your carrier/sim-card/mobile data ISP may not support it.
By the way, I am also having the same problem. WIfi connect to nextdns but mobile data says "couldn't connect". I think both of us are having the problem as mentioned above.