I have Ubuntu 18.04, Firefox 70.0.1 and every switch/select-box/radio works fine - I can only complain on italics off|auto|on configuration, because it's a bit slow (it does not change immediately, ~2s). I'd try to look into Developer Console first to investigate if all JSes were loaded and they haven't returned any error.

In Firefox Developer 71.0b7, it works for me on Windows 10, but not Windows 7. So maybe it has something to do with the OS?

Interesting! Android with Firefox Preview works fine for me.