"Funny" thing is that implementation in browser (as Mozilla is pushing now; or generally per-application) makes the least sense of all. Either I want to protect whole network, so I need it on router. Or I want to protect computer (better for mobile devices, because with them I don't always have control over network) and then I need system-wide solution there. Not only browsers use DNS.
And the idea with canary domain and ability to tell browser this way to not use DoH, it's not hard to predict how it will go, is it? If I'm the bad guy who wants to mess with users' DNS, of course I will use that.
People who quote full posts should be spanked with ethernet cable. Some exceptions for multi-topic threads may apply.