yandex Browser which also support every Chrome desktop extensions(looking at you ublock ...) on Android has this feature glad to hear I'm not the only one I use it.

I too wanted the same just write a small UserScript or just a ublock scriplet to modify viewport : function addViewport() { var metaTag = document.createElement('meta'); metaTag.name = "viewport"; metaTag.content = "width=device-width, initial-scale=0.45, maximum-scale=0.8, user-scalable=1"; document.querySelector('head').appendChild(metaTag); } document.addEventListener('DOMContentLoaded', function () { addViewport(); });

unfortunately dark reader makes Firefox too slow let's use stylus or https://github.com/m-khvoinitsky/dark-background-light-text-extension

it's not a bug (I'm a long time user and I compile fenix from source )a few about:pref are "locked " like ipc.processcount

happened to me too more than twice ...