nextdns can't block YouTube app on Android

Of course. No DNS provider can block Youtube ads. Pls use Youtube Revanced, it will do block ads well

Any app that connects to its HQ using a domain name URL needs a DNS resolver like NextDNS.

Apps that connect to its headquarters directly using its unique IP address do not pass through a DNS resolver like NextDNS.

To block apps using a direct IP connection without requiring a DNS resolver service, you will need a firewall.

DNS resolvers help block and filter DNS requests. Firewalls block IP addresses.