network.dns.forceResolve
Chrome desktop also has something like this, but it's a command-line option. Firefox OTOH allows one to select a global domain-to-IP mapping while the browser is running.
uMatrix and uBlock are IMHO designed for graphical browsers and the graphical www. For me, graphics are secondary, not a priority. I can get better (easier) control over HTTP requests and real-time transparency into TLS traffic through a forward proxy.
Firefox is still massive overkill for me. Ridiculously large and complicated. No doubt there are people who are comfortable and pleased with this sort of complexity. Glad they like it, but I am not one of those people.
Unlike Chromium or Firefox the relatively small and simple software I use to extract information from the web can be compiled in seconds on inexpensive hardware. The speeds of "no-browser" (HTTP generator plus TCP client) or the text-only browser I use easily beat any graphical, Javascript-running browser. Better control over HTTP headers, cookies and real-time, configurable logging. Not only that but I can process large, catenated HTML files that make the complex, popular browsers stall and choke.
If the goal is to achieve some customised graphical representation of a complex website, I think uBlock Origin and uMatrix are unmatched. But if the goal is "blocking", i.e., only making the HTTP requests that the user intends, and controlling the content of those requests, without regard for graphics, then I think I do better with the foward proxy.