

These people have no clue how to get around these DNS filters.
But not thanks to the virtue of some effective blocking but just a lack of knowledge of the average user…
I have used several of those cheap routers over the years. And they simply can’t block you from using encrypted DNS (unless they want to create giant blocklists and want to play wack-a-mole with DNS servers…).
So all they usually do is very low tech like ignoring the DNS you set in the router configuration and reroute it (or not providing such configuration in the first place). But they can effectively ony do so with unencrypted DNS.
With encrypted DNS they could at best try to block the default port used by DNSoverTLS but that still leaves DoH. And they can’t block that because it’s just regular encrypted HTTPS traffic (with the DNS quesry inside).
Iirc even Windows allows easy configuration of DoH nowadays (and for much longer if you were ready to edit the registry) where you can simply chose between unencrypted, DoH only or encryption preferred if available.




No.
Let’s Encrypt checks if you have control over the server the name eventually leads to, usually by providing you with a token that you put on your server for retrieval. The way there, including the IP, is irrelevant.