>Official Firefox can be leaky unless you build it yourself with some build-time changes or use a fork with such[0]. Am I guessing right that you still have Webcompat, RemoteSettings, and Nimbus enabled still? How do you know a compatibility intervention isn't causing your browser to open the kimono just enough to "unbreak the page"?

See my other comment, tor browser works fine too: https://news.ycombinator.com/item?id=48346659