I'm not sure what the commenter's setup is, but I have one that (at least mostly) achieves the same thing. It is a combination of a few things:
1. Redirect all outbound DNS traffic to your own local DNS server (as described in the link in this post)
2. Return NXDOMAIN for well-known DoH domains [1] (as well as "use-application-dns.net" for well-behaving software like Firefox [2])
3. Block traffic to well-known DoH providers by destination IP address [1]
Yep, pretty much the above - I have a combination of rules that control all traffic. Only the router is allowed to use port 53 outbound - all other traffic is redirected using NAT to the router's DNS server.
I mentioned Mikrotik previously - I use them myself.
1. Redirect all outbound DNS traffic to your own local DNS server (as described in the link in this post) 2. Return NXDOMAIN for well-known DoH domains [1] (as well as "use-application-dns.net" for well-behaving software like Firefox [2]) 3. Block traffic to well-known DoH providers by destination IP address [1]
[1] https://github.com/bambenek/block-doh [2] https://support.mozilla.org/en-US/kb/configuring-networks-di...