Thank you and previous poster for sharing how to get that working.
"about:config" just works in Nightly. No fuss.
You can sideload extensions in Nightly, too, after you activate the developer options. I don't think they've added that to regular, as yet? At least not with as much flexibility.
Anyway, I'm gonna try this mobile desktop mode thing and see how it goes. Thank you to everyone!
I think the only difference is nightly allows installing unsigned extensions, which I don't personally have a need for (as getting a personal/non-published extension signed is very easy).
quite likely that the site has a mobile "mode" and a small-screen mode (for desktop), each made by different teams. some mobile mode website is fine, but others suck. Where as the small-screen mode for desktop tend to be made by the same team/person as the main site (it's a css media query after all) - so it's likely to be more coherent.
Thanks for sharing.
Recently I've set up Firefox on Android so that it always run in desktop mode. I needed to also change screen width in about:config, because otherwise everything is too small. But after this websites seem to work better.