What exactly does 'this network blocks secure DNS traffic' mean?

Question

Domain Name System

There is a network in the apartment, connected to the provider. When the phone is connected to it, it displays the warning 'This network blocks secure DNS traffic'. Are we talking about the local network or the provider's network, where is it blocked? What exactly does this warning mean? The phone is able and wants to communicate using the secure DNS protocol, but they don’t give it to it? Or, as they say on the Internet, any member of the network can listen to DNS requests (I do not believe)? On the provider's side, traffic is not blocked: this functionality is simply not available. The router should not block either: there is AP Ubiquiti, it was installed 10 years ago.

Answer 1

Most likely, blocking by Roskomnadzor: https://habr.com/ru/news/t/577108/

Answer 2

Russian in white - this network blocks DoH and all sorts of other quirks of consciousness intended to bypass anoscopy by the RKN. It can also block public DNS. In general, as always, human laziness.
RKN decided to control traffic
But it turned out that it needed more resources
RKN decided to control only DNS
But there were people who raised DNS-over-HTTPS servers and public DNS
RKN decided to block DoH and public DNS servers
-- you are here ---
.. .

Answer 3

I am an employee of this provider, the client complained. Yes, I forgot about the TSPU installed in our country, which is controlled by Roskompozor :|