Me too before I made the config changes that I mention in that other post.
Now I get the joy of a local complaint that “thisiswhatitis” does not exist as a host on my network (although most people would instead get an error that DNS lookup on “thisiswhatitis” gave an error, presumably NXDOMAIN). No search occurs at all and, in my case, nothing is sent to the internet. Which is exactly what I want.
I think this illustrates that the sheer number and complexity of config changes that is required to make Firefox private is too high. I can understand that someone would decide that a different base would be a better starting point for a private browser. I concede that the blog post that I linked to is not an in-depth discussion of all the considerations that led to the decision to cease using Firefox.
In my opinion the problem is not exclusively one of the browser. Some privacy problems are inherent in HTTP / HTML. Hence the Back-to-the-Pleistocene movement of the web (Gemini).