Firefox Mobile (for Android), especially on Tablets, desperately needs the Desktop view Setting as an Toggle default option, with the choice of enabling it or disabling for the current website.
Reason for that is, that during the usage on Samsung DeX (I'd like to imagine that this is a rather neglected part of usage for many developers), the app is basically displayed as a mobile site like it was if it were to be in pop view, which is alright on mobile devices, but on Tablets, it's a necessity to set them straight as Desktop Windows.
Samsung own Browser has the ability to default into Desktop View, the only drawback is that the pinch zoom can't be disabled. It's possible, and I do believe it shouldn't take long for implementation.
(In the Screenshot provided it detects if it's in DeX mode or not, which isn't what I mean. A simple toggle would basically be this feature)